LASP THEMIS 2009 WORKSHOP
SESSION ABSTRACTS
Session A: Solar Wind, Foreshock, Bow Shock and Magnetosheath
Session B: Magnetopause, polar cusps and dayside aurora
Session C: Magnetotail, Plasma Sheet, Substorms and Nightside Aurora
Session D: Inner Magnetosphere, Radiation Belts, Plasmasphere
Session X: General Subject (Now part of AB)
SESSION A (3/7)
Interaction of a Reconnection Exhaust in the
Solar Wind with Earth's Bow Shock
Cheng-Chung Lin(1), Jih Kwin Chao(1), Lou-Chuang Lee(1),
Jih-Hong Shue(1), and Wen-Chieh Hsieh(1)
(1) Institute of Space Science, National Central University, Taiwan
Reconnection exhausts in the heliospheric current sheet (REHCS) have been recently
reported based on observations at and beyond 1 AU. Here we report an interaction of an
exhaust with the bow shock using multiple observations from the THEMIS, ACE, Wind,
Cluster, Geotail, and GOES 12 satellites. During the period of 12:57 UT on May 7, 2007,
ACE, a solar wind monitor, observed a reconnection exhaust. The exhaust continued
propagating through the bow shock and into the magnetosheath. During the event
THEMIS-E and Geotail stayed in the magnetosheath and observed the same exhaust.
These conjunction observations provide an excellent opportunity to study the properties
of the exhaust in the solar wind and those in the magnetosheath and compare their
differences. It is found that its spatial thickness decreases significantly after the REHCS
interacts with the bow shock, and the ratio of the guide field to the total magnetic field of
the REHCS also decreases. Some previous numerical simulations showed that the guide
field plays a crucial role in the generation of discontinuities associated with the
reconnection process.
THEMIS Observations of a Series of Hot Flow Anomaly Events
H. Zhang(1), D.G. Sibeck(1), Q.-G. Zong(2), J.P. McFadden(3),
K.-H. Glassmeier(4), J.W. Bonnell(3), and A. Roux(5)
(1) NASA Goddard Space Flight Center, Greenbelt, MD, USA
(2) Center for Atmospheric Research, University of Massachusetts-Lowell
(3) Space Sciences Laboratory, University of California,
Berkeley, California, USA
(4) Institute for Geophysics and Extraterrestrial Physics, TU
Braunschweig, Germany
(5) CETP, Velizy, France
A series of 7 Hot Flow Anomaly Events (HFAs) has been observed by THEMIS
spacecraft upstream in 12 hours on August 19, 2008. Both young HFAs (no shocks at
edges, two population in ion distribution) and mature HFAs (strong shocks at edges, one
hot population in ion distribution) have been observed. All 7 HFAs are associated with
strong (0.1 mV/m) electrostatic waves at two frequency bands, i.e., 128-256 Hz and 0.5-1
kHz. For young HFAs, electrostatic waves were observed throughout the events.
However these waves were only observed at edges of mature HFAs and strongly damped
at the center. The two possible electrostatic waves at these frequencies are ion acoustic
waves and lower hybrid waves and they are possible source of ion and electron heating
inside HFAs.
A Study of Electrostatic Turbulence in the Electron Foreshock Region
Based on the Evolution of Nonlinear Electrostatic Waves found in the
Electrostatic Shock Simulation
L.-H. Lyu(1), T.C Tsai(1), and W.C. Hsieh(1)
(1) Institute of Space Science, National Central University, Chung-Li, Taiwan, R.O.C.
Hot electrons in the downstream region of the perpendicular bow shock can escape to the
upstream side of the near-by oblique bow shock along the magnetic field line and form an
electron foreshock region in the solar wind. Nonlinear electrostatic turbulences are
commonly observed in the electron foreshock region. To understand the formation of
these nonlinear waves, we use a non-periodic Vlasov simulation code to simulate the
evolution of nonlinear electrostatic waves in the upstream and downstream regions of the
electrostatic shocks under different shock jump conditions. Our simulation results
indicate that a steady electrostatic potential jump can be formed within a few electron
oscillation periods after the hot downstream electrons meet the cold upstream electrons.
Different types of electron acoustic waves and ion acoustic waves are found in our
simulations. We will discuss the formation mechanisms of these nonlinear electrostatic
waves. We will also compare our simulation results with the electrostatic turbulence
observed by the THEMIS C satellite in the electron foreshock region.
SESSION B (9/7)
Testing predictions of the Reconnection Location with THEMIS
K.J. Trattner(1), S.M. Petrinec(1), S.A Fuselier(1) and T.D. Phan(2)
(1) Lockheed Martin ATC, 3251 Hanover St., B255, ADCS, Palo Alto, CA 94304-1191
(2) Space Sciences Laboratory, University of California, Berkeley, CA, USA.
Recent studies concerning the location of the reconnection line with single point
measurements under stable solar wind and IMF conditions reveal that magnetic
reconnection tends to occur along a continuous X-line of maximum magnetic shear
across the dayside magnetopause. Exceptions to this continuous reconnection X-line are
dominant southward IMF conditions (within ±25° of southward IMF) or a dominant IMF
Bx component (more than 70% of the IMF in the Bx component) for which the
reconnection line bifurcates, and exists along magnetopause regions where the merging
fields are exactly anti-parallel. In this presentation we will discuss plasma observations at
the magnetopause by the THEMIS satellites. On 2 occasions, the spacecraft observed in
the boundary layer accelerated flows that switched directions as the spacecraft crossed
the magnetopause. These accelerated flow reversals indicate that the reconnection line
was very close to the spacecraft. The observed positions of the reconnection lines are
compared with prediction from the maximum magnetic shear model. In both cases the
observed location is in agreement with the model prediction. However, in the second case
the model predicted an anti-parallel reconnection site; indicating that the solar wind
conditions responsible for transitioning between the anti-parallel reconnection scenario
and the tilted X-line need further investigation.
Uneven Compression Levels of Earth's Magnetic Fields by
Shocked Solar Wind Due to Magnetic Reconnection
J.-H. Shue(1), Y.-S Chen(1), W.-C. Hsieh(1), M. Nowada(1),
B.S. Lee(1), P. Song(2), C.T. Russell(3), V. Angelopoulos(3),
K.H. Glassmeier(4), J.P. McFadden(5), and D. Larson(5)
(1) Institute of Space Science, National Central University, Jhongli, Taiwan
(2) Center for Atmospheric Research, University of Massachusetts,
Lowell, Massachusetts, USA
(3) Institute of Geophysics and Planetary Physics, University of
California, Los Angeles, California, USA
(4) Institute of Geophysics and Extraterrestrial Physics,
Technical University Braunchweig, Braunchweig, Germany
(5) Space Sciences Laboratory, University of California,
Berkeley, California, USA
The magnetopause is the boundary where the reduced solar wind dynamic pressure by the
divergence of the magnetosheath flow is balanced by the magnetic pressure of the
compressed magnetosphere. With the aid of hundreds of magnetopause crossings
identified from the THEMIS spacecraft, we estimate the ratio of the compressed
geomagnetic field just inside the subsolar magnetopause to the dipolar magnetic field
using THEMIS observations and the theoretical dipolar magnetic field model. Previous
studies reported that the ratio is independent of the subsolar standoff distance. Here we
find that the ratio is linearly proportional to the subsolar standoff distance for southward
interplanetary magnetic field, a favorable condition for an occurrence of the magnetic
reconnection at the magnetopause.
Dependence of Magnetopause Oscillation Frequencies
on Solar Wind Conditions
F. Plaschke(1), K.-H. Glassmeier(1), D.G. Sibeck (2), H.U. Auster(1),
O.D. Constantinescu(1), V. Angelopoulos(3), W. Magnes(4), and J.P. McFadden(5)
(1) Institut fur Geophysik und Extraterrestrische Physik, TU Braunschweig,
Germany
(2) NASA, Goddard Space Flight Center, Maryland, USA
(3) Institute of Geophysics and Planetary Physics, University of California,
Los Angeles, California, USA
(4) Space Research Institute, Austrian Academy of Sciences, Graz, Austria
(5) Space Sciences Laboratory, University of California, Berkeley, California,
USA
The pearls-on-a-string coast phase configuration of the five THEMIS probes facilitated
the reconstruction of magnetopause (MP) motion during the first several months of
operation in 2007 via spline interpolation. From these interpolations oscillation
frequencies could be inferred. The distribution of these frequencies displays local
maxima at some frequencies belonging to a set of stable and recurrent (so-called "magic")
frequencies of ULF geomagnetic pulsations, which were found to appear with an
enhanced occurrence probability. These findings were related to the existence of MP
surface wave eigenmodes (standing Alfven waves on the MP). However, oscillations
generated by many different effects may actually contribute to the observed frequency
distribution. Using solar wind magnetic field and flow velocity data from the OMNI
database for the time intervals of concern as well as local time information of the
corresponding MP oscillation locations we are able to further discriminate between
oscillation events with regard to different generation effects. Our results are favorable to
the interpretation of the predominant frequencies in terms of MP surface eigenmodes
supporting the concept of the MP being a membrane under tension.
Evolution of Crater Flux Transfer Events into Typical Ones
H. Zhang(1), M.G. Kivelson(1), K.K. Khurana(1), V. Angelopoulos(1),
T. Phan(2), J. McFadden(2), K.H. Glassmeier(3) and H.U. Auster(3)
(1) Institute of Geophysics and Planetary Physics, University of California,
Los Angeles, California, USA
(2) Space Sciences Laboratory, University of California, Berkeley,
California, USA
(3) Institut für Geophysik und Extraterrestrische Physik, TUBS,
Braunschweig, Germany
Transient bipolar perturbations of the magnetic field normal component are frequently
encountered on the dayside magnetopause. Often the field magnitude increases to a peak
at the center of the bipolar normal signatures. In the literature such signatures are
identified as "flux transfer events" (FTEs). In some cases the field magnitude increase
shows a crater-like dimple in the center and is referred to as a "crater FTE". Behind the
phenomenological definitions, there lie two physical interpretations: a typical FTE is a
flux rope with strong core field compressed by the curvature force of surrounding twisted
fields; a crater FTE represents a flux rope with a weak core field that through the
presence of enhanced plasma pressure at the core of the flux rope balances the inward
forces deriving from the magnetic tension of the surrounding twisted fields. It has been
suggested that the signature of a crater FTE, identified in single spacecraft data, could be
mimicked if the spacecraft trajectory passed through a depression on the magnetopause
moving from the magnetosphere to the magnetosheath and then back to the
magnetosphere. Only observations from multiple spacecraft with appropriately
distributed impact parameters can distinguish a passage through a crater FTE from a
passage through a perturbed magnetopause. In this study, we survey all the data recorded
by multiple THEMIS spacecraft near the dayside magnetopause from May to October in
2007. We find that typical FTEs with central peaks are commonly embedded in
depressions of the magnetopause. We also present several crater FTE events in which the
flux rope structures with weak core fields are confirmed by multiple THEMIS spacecraft
observations. We notice that, in the time interval examined, the crater FTEs are observed
much less frequently than typical FTEs. The infrequent encounters with crater FTEs can
be understood if they are finite in the axial direction and if non-uniform curvature stress
generates field-aligned pressure gradients and associated flow along the axis and out of
the flux rope. With this interpretation, the crater FTE would not be a steady structure and
it would eventually evolve into a typical one.
Concerning the Orientation and Motion of FTEs on the
Dayside and Flank Magnetopause
D. G. Sibeck(1), and R.-Q. Lin(2)
(1) NASA/GSFC, Greenbelt, MD 20771, USA
(2) NSWC, Carderock, MD 20817, USA
We employ the Cooling et al. [2001] model for magnetosheath plasma and magnetic field
parameters to determine the motion and orientation of FTEs initiated along one or more
extended reconnection lines passing through the vicinity of the subsolar magnetopause
with initial tilts determined by the IMF orientation. When the IMF points strongly
southward, the events accelerate rapidly antisunward over the polar caps. When the IMF
points strongly northward, they move much more slowly around the magnetospheric
flanks. In both cases, event orientations remain almost unchanged as they move away
from the reconnection line. With the help of analytical models for the magnetosheath and
magnetospheric magnetic fields, we evaluate the strength and direction of the
perturbations that the FTEs generate in the surrounding media. Events that pass almost
unnoticed on the dayside magnetopause during periods of northward IMF orientation
become much more prominent as they move into the differing magnetic field orientations
that characterize the flank magnetopause. Events that occur on the flanks during periods
of southward IMF orientation must be generated locally, because they cannot originate at
dayside reconnection lines. Finally, the results from this analysis suggest that observation
of the flow perturbations generated by FTEs in the surrounding media can generally be
directly associated with the initial reconnection line orientation.
Magnetic Island Formation at an Undulating Flank Magnetopause
Beyond the Duskside Terminator
S. Eriksson(1), W.-L. Teh(1), H. Hasegawa(2), B.U.O. Sonnerup(3),
J.P. McFadden(4), K.-H. Glassmeier(5), O. Le Contel(6), V. Angelopoulos(7),
D.E. Larson(4), R.E. Ergun(1), and C.W. Carlson(4)
(1) Laboratory for Atmospheric and Space Physics, University of
Colorado, Boulder, Colorado, USA
(2) Department of Space Plasma Physics, Institute of Space and
Astronautical Science, Japan Aerospace Exploration Agency,
Sagamihara, Japan
(3) Thayer School of Engineering, Dartmouth College, Hanover, New
Hampshire, USA
(4) Space Sciences Laboratory, University of California, Berkeley,
California, USA
(5) Institut fur Geophysik und Extraterrestrische Physik, Technische
Universitat, Braunschweig, Germany
(6) Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau,
France
(7) Institute of Geophysics and Planetary Physics, University of
California, Los Angeles, California, USA
THEMIS multi-spacecraft observations on 8 June 2007 showed that small magnetic
islands preferentially occurred at the sunward facing edges of postnoon magnetopause
surface waves in the presence of a low-beta plasma depletion layer (PDL). This may be
understood in terms of a local compression of the magnetopause current sheet by the
action of neighboring large-scale Kelvin-Helmholtz (KH) vortices. Here, we extend this
study and present a similar KH-like magnetopause event that occurred for northward
IMF, but beyond the duskside terminator on 15 April 2008. We examine Grad Shafranovlike and MHD reconstructions based on TH-C data during two bipolar events at ~0834
and ~0837 UT when TH-B was in the adjacent magnetosheath and provided local IMF
information. We examine the particle burst data at the time of these two small-scale
islands for any evidence of reconnection-related signatures and investigate whether a
PDL and its low plasma beta is a necessary condition for the formation of these smaller
scale magnetic islands.
THEMIS Observations of Particles and Fields in the Vicinity of X-lines
at the Dayside Magnetopause
Tai Phan(1), Masaki Fujimoto(2), Vassilis Angelopoulos(3), Jim McFadden(1), Davin
Larson(1), Marit Oieroset(1), Jonathan Eastwood(1), John Bonnell(1), Forrest Mozer(1),
and Karl-Heinz Glassmeier(4)
(1) SSL, University of California, Berkeley, CA, USA
(2) JAXA/ISAS, Japan
(3) IGPP, University of California, Los Angeles, CA, USA
(4) IGEP, TU Braunschweig and MPS, Katlenburg-Lindau, Germany
We will discuss burst-mode observations in the vicinity of X-line crossings at the
magnetopause. Of particular interest are electron signatures which provide information
on field-line topology as well as the history of reconnection.
A Statistical Study of the Reconnection Exhaust of the Dayside
Magnetopause: Can Any of These Satellite Paths Have Passed
Through the Reconnection Diffusion Region?
L. Andersson(1), S. Eriksson(1), R.E. Ergun(1), and J. Tao(1)
(1) LASP/University of Colorado, Boulder
This paper is focusing on when the Themis satellites where close to the sub-solar point
recording magnetopause crossings identified by a sign change in the magnetic field Bz
component at the time when the satellite moved between a magnetospheric and a
magnetosheath type of plasma. Resent results from Cluster and Themis have suggested
that asymmetric reconnection is taking place at the magnetopause and those studies have
presented some of the features of the exhaust. We present here a statistical study based on
175 Themis crossings focusing on particle, magnetic field, density and "medium"
resolution electric field data. Some of the results can be concluded as follows. The
particle distributions in the exhaust may sometimes be associated with positive slopes in
the particle distribution functions which indicate unstable plasmas. Not all crossings have
a significant density gradient associated with them. Not all crossings have a significant
magnetic field gradient associated with them. Finally, the main accelerated population in
the exhaust is magnetosheath type plasma. This statistical study suggests that observing
the exhaust is trivial but observing the reconnection site itself is hard. The paper calls out
for better understanding how to uniquely identify the reconnection site based on
observables.
Possible Magnetospheric Kelvin-Helmholtz Vortices Detected by
THEMIS near the Post-Noon Magnetopause
F. Palermo(1), F. Califano(1), O. Le Contel(2*), V. Angelopoulos(3),
K.-H. Glassmeier(4), U. Auster(4), J. McFadden(5), D. Larson(5), J.W. Bonnell(5),
C. Cully(6), R. Ergun(7)
(1) Physics Department, University of Pisa, Italy
(2) LPP, CNRS/Ecole Polytechnique/UPMC, France
(3) IGPP, UCLA, USA
(4) TUBS, Germany
(5) SSL, UCB, USA
(6) Swedish Institute of Space Physics, Sweden
(7) LASP, University of Colorado, USA
We report on possible magnetospheric Kelvin-Helmholtz (KH) vortices detected by
THEMIS near the post-noon magnetopause. Oscillations of the magnetic field and of the
ion velocity with a period around 7 minutes are measured. Minimum variance analysis
(MVA) seems to indicate that the oscillations could correspond to surface waves
propagating along the magnetopause. In the MVA frame, the magnetic field and ion
velocity data display vortex-like signatures. Yet ion spectrograms show no
magnetosheath/magnetosphere plasma mixing and these vortices appear as purely
magnetospheric vortices. Numerical simulations of the KH instability are presented to
support this possibility.
SESSION C (38/26)
Plasma Sheet Dynamics Imposed by Bursty Bulk Flows
E.V. Panov(1), R. Nakamura(1), W. Baumjohann(1), V.A. Sergeev(2), T. Takada(3),
M. Volwerk(1), A. Retinó(1), K. Keika(1), V. Angelopoulos(4), C.T. Russell(4),
K.-H. Glassmeier(5), H.U. Auster(5), K.-H. Fornaçon(5), J.W. Bonnell(6),
J.P. McFadden(6), C.W. Carlson(6), D. Larson(6), I. Mann(7)
(1) Space Research Institute, Austrian Academy of Sciences, Graz, Austria
(2) St. Petersburg State University, St. Petersburg, Russian Federation
(3) Institute of Space and Astronautical Science, Sagamihara, Japan
(4) Institute of Geophysics and Planetary Physics,
University of California, Los Angeles, CA, USA
(5) Institut für Geophysik und extraterrestrische Physik,
Technische Universität Braunschweig, Germany
(6) Space Science Laboratory, University of California, Berkeley, CA, USA
(7) Department of Physics, University of Alberta, Edmonton, Alberta, Canada
On 17 March 2008 around 9:12 UT the five Themis spacecraft were located in the plasma
sheet no more than 1 hour MLT apart and covered radial distances from 15 Re (THB) to
about 10 Re (THA). We found that all the spacecraft consecutively observed a bursty
bulk flow traveling first earthward, slowing down between THB and THA from 400 km/s
to 50 km/s, and then changing toward the opposite direction. We found that the most
tailward located spacecraft, THB and THC, detected thinning and then thickening of the
plasma sheet around the time of the flow direction change. The plasma sheet thinning
propagated from THB to THC at about the Alfvén velocity in the plasma sheet boundary
layer. Both spacecraft showed signatures of crossing the reconnection separatrix. On the
other hand, we found that the THA, THD and THE spacecraft, which were located in a
more dipolar region, indicated first plasma sheet thickening and then thinning. The five
spacecraft observations can well be explained as the observation of the reconnected
magnetic flux, which first moved toward a more dipolar field region close to the Earth,
and then bounced tailward. Finally, we discuss the Pi2 pulsations observed by ground
based magnetometers during these space observations, and also the non-adiabatic heating
of particles inside the plasma sheet found after the sheet's thinning-thickening motion.
Some Recent Results on Current
Disruption/Dipolarization from THEMIS
A.T.Y. Lui(1)
(1) JHU/APL, Laurel, MD 20723-6099, USA
Current disruption/dipolarization observed by THEMIS during an isolated substorm is
investigated in detail. An inverse cascade in energy of fluctuating fields is evident in this
event. The electromagnetic waves excited initially are identified through analysis of the
fluctuating fields to be obliquely propagating ion cyclotron waves, which are shown to be
consistent with waves generated by the Alfvén-ion-cyclotron instability. There is
evidence that the frozen-in condition is violated during this interval.
Multi-scale Analysis of Reconnection and Current Disruption
Associated Fluctuations during Magnetospheric Substorms
Z. Voros(1), A. Runov(2), V. Angelopoulos(2), M.P. Leubner(1),
W. Baumjohann(3)
(1) Institute of Astro- and Particle Physics, University of Innsbruck,
Innsbruck, Austria
(2) Institute of Geophysics & Planetary Physics,
University of California, Los Angeles, USA
(3) Space Research Institute, Austrian Academy of Sciences, Graz, Austria
We present multi-scale fluctuation signatures of some well-documented substorm events
from the THEMIS mission when the observations over multiple locations indicated the
occurrence of both mid-tail and near-Earth activations. Multi-scale methods allow
identifying the scales of energization and in combination with the timing analysis lead to
better description of energy redistribution during substorms.
Relation of High Speed Flows to Dipolarization
at the Inner Edge of the Plasma Sheet
R.L. McPherron(1), T-S. Hsu(1), V. Angelopoulos(1), and the Themis Team
(1) Institute of Geophysics and Planetary Physics, University of California, Los
Angeles, USA.
High speed flows and fluctuating dipolarization of the magnetic field are frequently seen
by Themis D and E at the inner edge of the plasma sheet. Such observations have been
interpreted as current sheet disruption and suggested to be the trigger for substorm onset.
We use observations from Themis D to study the association of flows and dipolarization,
the location of these events, and their relation to substorms. We find that dipolarization
and flows are closely related. On the average perturbations in earthward flow precede the
onset of major increases in the Z-component of the magnetic field by one minute. Flows
and dipolarization events are peaked at ~10 Re in the sector from about 22 LT to 01 LT.
Many dipolarization events are preceded by a sudden decrease in Bz that begins at the
time of the initial flow perturbation or shortly later.
Observations of Auroral Activations and Fast
Flows on Feb. 16, 0220 UT Substorm
R. Nakamura(1), V. Angelopoulos(2), H. Frey(3), W. Baumjohann(1),
W. Magnes(1), K. Keika(1), S. Kiehas(1), V. Ivanova(1), E. Panov(1),
A. Runov(2), K.-H. Glassmeier(4), U. Auster(4), J. McFadden(3),
D. Larson(3), J. Bonnell(3), S. Mende(3), E. Donovan(5), H. Singer(6),
C. T. Russell(2), I. Mann(7), O. Amm(8), and J. Weygand(2)
(1) IWF/OEAW, Austria
(2) IGPP/ UCLA, Los Angeles, USA
(3) SSL/UCB, Berkeley, USA
(4) TUBS, Braunschweig, Germany
(5) U Calgary, Calgary, Canada
(6) NOAA/SEC, Boulder, USA
(7) Univ. Alberta, Edmonton, Canada
(8) FMI, Helsinki, Finland
We compare and contrast the possible field-aligned current signaturesassociated with
dipolarization accompanied by Earthward flows during two auroral activations with
poleward/equatorward expansion starting around 0216 UT and 0243 UT on 16 Feb 2008,
when the five THEMIS spacecraft were distributed in the premidnight to midnight (22-24
MLT) region between 8 and 18 RE downtail. Clear dipolarizations associated with
Earthward flows were observed at the THD(P3) and THE(P4) spacecraft in the
premidnight sector at downtail distances between 8 and 9 RE, when the mid-tail
spacecraft, THC(P2) and THB(P1), provided information on the current sheet
configuration. Both dipolarization events started from the tailward side, THD(P3), but
had quite different profiles in the magnetic shear components relevant to the field aligned
current, as well as in the magnetotail current sheet configuration and auroral signatures.
The 0216 UT event occurred in a thinner near-Earth current sheet condition and THD(P3)
and THE(P4) detected depolarization accompanied by fast flows and enhanced shear in
the magnetic field, while conjugate ground signatures suggest development of a slant
North-south aligned aurora, east of a small surge. During the 0243 UT event, X-line
signatures at a midtail thin current sheet were observed, followed by a large-scale plasma
sheet expansion and the associated auroral activation took place more poleward.
Dipolarization was again observed at THD(P3) and THE(P4) but accompanied by less
significant shear component. We discuss these two different dipolarization/field aligned
current signatures in terms of different stages of the fast flows interacting with the
ambient field in a different configuration of the tail current sheet.
Recommendations Concerning the
Substorm Onset Timing Studies Using Themis
V.A. Sergeev(1)
(1) St.Petersburg State University, St.Petersburg, Russia
The major goal of Themis project is to distinguish between In-Out and Out-In scenarios
of substorm initiation and to decide on the substorm onset process. Timing of substorm
onset features using unprecedented space and ground coverage provided by the Themis
during its major conjunctions seems to be the main way to reach this goal. However the
final result may appear only after assembling the individual event studies performed by
different groups, which implies a necessity of a common timing framework. Such
framework should include the minimal positional, timing and intensity information
sufficient to decide on the quality of the conjunction in different aspects, on the intensity
of the event and of its particular key manifestations, and make possible to combine and
analyse together all collected events to perform a concluding statistical analyses. To
initiate the discussion we circulated a draft which is also placed on the web at:
http://geo.phys.spbu.ru/themis/timing_requirements/Timing_requirements_v00.htm
After collecting and summarizing the comments to this draft (please, send them to me by
e-mail) we suggest discussing this issue at the Boulder 2009 Themis workshop to end up
with the recommendations, and to suggest an effective way how to combine the efforts of
different groups to reach the goal.
Plasma Properties of Substorm Current Wedge Associated
Dipolarizations at the Entry to the Inner Magnetosphere
V. Sergeev(1), S. Dubyagin(1), S. Apatenkov(1), T. Sugak(1),
V. Angelopoulos(2), J. McFadden(3), D. Larson(3), and J. Bonnell(3)
(1) St.Petersburg State University, St.Petersburg, Russia
(2) IGPP/UCLA, Los Angeles, USA
(3) UC Berkeley, Berkeley, USA
We summarize recent results of studying the SCW-related dipolarizations observed by
Themis spacecraft between 6 and 12 Re in equatorial region to emphasize the following
features: (1) Statistically a comparison of near-equilibrium configurations before and
after the dipolarization indicates the growth of plasma pressure, but a decrease of plasma
entropy after the dipolarization. (2) Timing at radially-separated spacecraft pair for the
sharp dipolarization fronts (SDF) with well-defined Earthward normals gives the inward
velocities of 100-300 km at r~8-10Re. (3) At the periphery of the quasi-dipolar region
(between 8 and 11Re), where the steady Earthward B- and pressure gradients are
observed, the major plasma response to dipolarizations consists in the plasma pressure
increase, decrease of plasma tube entropy and density, combined with the increase of
plasma temperature and high energy particle flux. Prior to the SDF arrival the large scale
modest increase of plasma flow and pressure (up to 20-30%) is observed for ~1min, with
perturbation propagating at nearly fast wave speed. Very different, the dipolarization
front propagates radially at much slower speed and, following its arrival, the plasma
entropy decreases and flow intensifies but looses coherence at closely-spaced spacecraft.
We interpret this Stage 2 as an encounter with the under populated plasma structure,
which is distinct also by its highly structured/granulated plasma proper. The Stage 1 (predipolarization) may then be understood as its sheath-like interaction region. The energetic
particle flux is usually most dramatically increased at the SDF but it actually can start to
increase at the pre-dipolarization stage 1. We briefly discuss the implications of these
observations for the mechanism of injections.
MHD Travel Time in the Magnetotail and its
Implications for Timing of Substorm Processes
P.J. Chi(1), and M.G. Kivelson*(1)
(1) Institute of Geophysics and Planetary Physics, UCLA, USA
An accurate estimate of the time required for a disturbance in the magnetotail to
propagate to the ionosphere is needed in order to establish the time history of phenomena
related to substorms. Recent THEMIS observations of the 26 February 2008 substorm
have found that the time delay from a substorm onset at X=-20 RE in the magnetotail to
the corresponding auroral intensification in the ionosphere can be as short as 96 sec,
calling into question whether or not Alfven waves can propagate fast enough to serve as
an agent connecting the two phenomena. Using empirical models of magnetic field and
plasma parameters, we have calculated the minimum time for an MHD wave to travel
from a substorm onset in the magnetotail to the ionosphere. The shortest time delay can
be shown to correspond to propagation along the so-called Tamao travel path, which
consists of an earthward-propagating segment in the equatorial plane in which the
disturbance is carried by the fast mode and a field-aligned route to the ionosphere in
which the disturbance propagates in the Alfven mode. Our results show that the travel
time of an MHD wave along the Tamao path is a strong function of the source location
and the latitude of the ground observer. For a source at X=-20 RE, the Tamao travel time
can be as short as 90 sec to ground stations connecting to magnetic field lines within 10
RE but outside the plasmasphere. It is therefore feasible for an impulse generated by a
substorm onset at X=-20 RE to be carried by MHD waves and reach the ionosphere
within 100 sec. However, travel delays on paths to the high-latitude ionosphere and the
low-latitude ionosphere are longer. The dependence of the Tamao travel time on
observer's latitude could also contribute to a commonly observed substorm phenomenon
that auroral intensification is first observed at low auroral latitudes and migrates poleward
in the following 1-2 minutes.
Calculations of E+VxB during Dipolarization Events
J.P. McFadden(1), D. Larson(1), J. Bonnell(1), F. Mozer(1), V. Angelopoulos(2),
K.-H. Glassmeier(3), and U. Auster(3)
(1) University of California, Berkeley, USA
(2) University of California, Los Angeles, USA
(3) Technische Universitat Braunschweig, Germany
During the first THEMIS tail season, we found that E+VixB was near zero for most of
the dipolarization events observed by TH-E near midnight at ~10 Re. Sustained non-zero
values for E+VixB were found during the substorm growth phase as the current sheet
thinned. For these data, abs(VixB)>>abs(E) suggesting that the non-zero E+VixB values
are due to diamagnetic drift associated with ion pressure gradients in the plasmasheet.
Other non-zero E+VixB values were observed at transient ion pressure gradients with the
abs(VixB) generally larger than the abs(E), also suggesting diamagnetic drift. For
pressure gradients where abs(E)>>abs(VixB), and where reliable electron data were
available, it was found that E+VexB was zero within the measurement error. These
observations suggest that non-zero values for E+VixB during substorm dipolarization at
~10 Re are primarily due to the JxB/en term in the generalized Ohm's law. This paper
will present further tests of the frozen-in condition from additional satellites during the
first and second tail seasons.
What do TCRs Tell us About Magnetic Reconnection?
S.A. Kiehas(1), V.S. Semenov(2), V.V. Ivanova(1), V. Angelopoulos(3),
R. Nakamura(1), H.K. Biernat(1,2), W. Baumjohann(1)
(1) Space Research Institute, Austrian Academy of Sciences, Graz, Austria
(2) Institute of Physics, State University, St. Petersburg, Russia
(3) Institute of Geophysics and Planetary Physics, ESS, UCLA, USA
(4) Institute of Physics, University Graz, Austria
We use TCR events during the first THEMIS tail season in 2008 and apply results from
an analytical time-dependent reconnection model to these events. The typical TCRrelated bipolar signature of Bz, but also signatures in Bx and vz, can be used to get
information about the reconnection process. Due to magnetic reconnection, outflow
regions of accelerated plasma propagate along the current sheet into the tail and towards
the Earth. These regions compress the magnetic field above and beneath them, leading to
travelling compression regions (TCRs) of magnetic field lines. The disturbances in the
plasma and the magnetic field, caused by the pass-by of the outflow regions, are used to
determine the amount of reconnected magnetic flux and where reconnection was
initiated. We show that TCRs can be seen as transporter of magnetic energy, which is in
the order of the kinetic energy of the plasma in the associated outflow region. This field
energy is directly related to the reconnection process and represents a non-negligible part
of the energy released during the reconnection process, which should be taken into
account.
Isotropic Boundaries in Different Magnetic Field
Models and in Observations
M. Kubyshkina(1), V. Sergeev(1), I. Shevchenko(1), and V. Angelopoulos(2)
(1) St.Petersburg State University, Russia
(2) UCLA, USA
Though mapping from magnetosphere to ionosphere (and back) along the magnetic field
lines remains one of the crucial questions of THEMIS mission, it's still rather difficult to
answer the question about the accuracy of mapping with a concrete magnetic field model.
There is no reliable criterion, which would help to evaluate the differences in model
predictions compared to the real projections. One of possible estimates for mapping
accuracy may be obtained from analyzing Isotropic Boundaries (IB) positions for the
particles of different energies, which are observed routinely by low-altitude spacecraft
(NOAA, DMSP). These observations may be compared with model predictions for IB
position and the difference between the modeled and observed latitudes of IB may serve
as a test for accuracy in mapping with a given model. For THEMIS tail season 2008 we
constructed a set of adjusted models (AM01, AM02), which are based on T96, but use as
input parameters those parameters that give best fit to THEMIS observations in a given
time period (instead of real Solar wind parameters). It appeared that mapping with AM01
and AM02 may differ as much as several degrees from that obtained with standard model
T96. Thus we need to answer a question: if the models give notably better magnetic field
representation in several points along magnetospheric tail, does that mean that mapping
will also be better with these models? In order to evaluate mapping quality of a number
of magnetospheric magnetic field models (T89, T01, T96 and it's modifications AM01,
AM02) we study Isotropic Boundaries locations, calculated for each model and compare
the results with available observations during THEMIS tail season 2008. We study the
performance of the models in different local time sectors and during the periods with
different activity levels.
Statistical Study of the Time Sequence of Substorm Onset-Related
Phenomena due to Global Alfvénic Interaction
Naiguo Lin(1), H. Frey(1), S. Mende(1), F. Mozer(1), R. Lysak(2),
Y. Song(2), and V. Angeloupolos(3)
(1) Space Sciences Laboratory, University of California, Berkeley
(2) School of Physics and Astronomy, University of Minnesota
(3) IGPP, UCLA
Observational timing sequences of substorms under various onset mechanisms are
examined by performing a statistical analysis, in which the occurrence times and
locations of onset-related phenomena observed in space and on the ground are organized
in a space-time diagram. The results show that substorm triggering processes may occur
throughout the stressed tail current sheet, and cause the breakdown of the frozen-in
condition in multiple active localized regions. The disturbance onsets at those active
locations may occur without obvious causal relationships between them. The results are
to some extent consistent with the suggestion that the substorm onset is the result of
Alfvénic interactions in the global current system. The rationale behind the use of the
space-time diagram in the study of substorm timing will be discussed.
Responses of Energetic Particle Fluxes from THEMIS and
Geosynchronous Observations to Substorm Onsets
during the Storm Main Phase
Ching-Huei Lin(1), and Kaiti Wang(2)
(1) Department of Electrical Engineering, Ching Yun University,
Jung- Li, 32097, Taiwan
(2) Plasma and Space Science Center, National Cheng Kung
University, Tainan, 70101, Taiwan
Variations of energetic particle fluxes from geosynchronous and THEMIS observations
are examined to investigate their responses to the substorm onset during the storm main
phase. Particle data provided by THEMIS mission including energy fluxes and angular
distributions will be analyzed for both ions and electrons at lower energy (< 30 keV) and
higher energy (> 30 keV) from the instruments ESA and SST, respectively. The
geosynchronous energetic particle fluxes observations provided by LANL satellites will
also be explored as complementary data. As to the magnetic field configuration, local
fields detected from THEMIS as well as geosynchronous fields observed from GOES
will be adopted. To consider the effect from solar wind parameters, the upstream solar
wind data from ACE is also applied to identify the magnetospheric environment. Phase
relation between energetic particle fluxes from LANL (at 6.6Re) and from THEMIS
(>12Re) was found to be reverse in the primary analysis.
Tailward Propagation of Dipolarization
Following Earthward Fast Flows
T. Takada(1), Y. Miyashita(1), H. Hasegawa(1), M. Fujimoto(1),
D.H. Fairfield(2), and V. Angelopoulos(3)
(1) JAXA/ISAS, Japan
(2) NASA Goddard Space Flight Center, USA
(3) IGPP, UCLA, USA
On 17 March 2008, the THEMIS and Geotail spacecraft were all located in the nearEarth magnetotail at X=-8 to -14 RE with separations of <4 RE in Y where they observed
earthward fast flows followed by dipolarization. The multi-spacecraft observations show
that the leading edge of the earthward fast flow propagated earthward (600-800 km/s)
into at least X=-9 RE, followed by the dipolarization which progressed tailward (200-400
km/s), suppressing the earthward flows. Subsequently, the active flow period gradually
ended starting on the earthward side after the enhancement of westward auroral
electrojet, indicating that the stabilization of the plasma sheet began at the near-Earth
plasma sheet and progressed tailward during the recovery phase. Associated with
propagation of an earthward flow region, the BZ drop was observed before the BZ
enhancement and propagates earthward with the cross-tail current enhanced, and leading
to the significant acceleration of the thermal electrons afterwards. The formation of such
BZ signatures, which was previously interpreted as a signature of the so-called explosive
growth phase, thus results from the propagation of an earthward flow region compressed
by the following earthward flows and the strong dipole field, rather than the "phase".
The present observation reveals the spatio-temporal development of the near-Earth tail in
the course of dipolarization.
SuperDARN Observations of ULF Pulsations during a Substorm
Expansion Phase Onset at 0437 UT on February 22nd 2008
N.A. Frissell(1), J.B.H. Baker(1), J.M. Ruohoniemi(1), R.A. Greenwald(1),
I.J. Rae(2), Z.C. Kale(2), L. Kepko(3), M.Lester(4), A. Grocott(4),
T.K. Yeoman(4), and S.E. Milan(4)
(1) Bradley Department of Electrical and Computer Engineering, Virginia Tech
(2) Department of Physics, University of Alberta
(3) Space Science Center, University of New Hampshire
(4) Department of Physics, University of Leicester
In support of THEMIS mission goals, the SuperDARN radar community is using a
special mode to maximize temporal resolution during THEMIS substorm events. The socalled "THEMIS mode" interleaves 8-second dwells on a single camped beam between
each successive beam of the normal 2-minute azimuth scan. In this way, the radars are
able to simultaneously provide: (1) measurements over a wide spatial area for
hemispheric context of ionospheric convection and (2) higher temporal resolution on a
single camped beam for examining pulsation phenomena. In this paper, we present
camping beam measurements from the Blackstone radar during the onset of a substorm
expansion phase identified by THEMIS spacecraft at 0437 UT on February 22nd 2008. A
comparison of the 8-second camping beam data with the 2-minute data on neighboring
beams demonstrates quite dramatically the new capability of the SuperDARN THEMIS
mode to routinely capture ULF pulsations. Spectral analysis shows that the velocity
oscillations seen by the radar during this particular event are in phase with magnetic
pulsations seen by nearby ground-based magnetometers. This is consistent with the
pulsations being associated with Alfven waves. Cross-phase analysis of the ground-based
magnetometer data suggests that the pulsations measured by the radar are in the vicinity
of the plasmapause.
Analysis of Recent Substorm Events and Relation to
Electromagnetic Wave Activity
O. Le Contel(1), A. Roux(1), C. Jacquey(2), P. Robert(1), V. Angelopoulos(3),
C. Cully(4), R. Ergun(5), J.W. Bonnell(6), K.-H. Glassmeier(7), U. Auster(7),
J. McFadden(6), D. Larson(6), H. Frey(6), S. Mende(6), E. Donovan(8),
I. Mann(9), C.T. Russell(3), H. Singer(10)
(1) LPP, CNRS/Ecole Polytechnique/UPMC, France
(2) CESR, CNRS, France
(3) IGPP, UCLA, USA
(4) Swedish Institute of Space Physics, Sweden
(5) LASP, University of Colorado, USA
(6) SSL, UCB, USA
(7) TUBS, Germany
(8) University of Calgary, Canada
(9) University of Alberta, Canada
(10) NOAA/SEC, Colorado, USA
Using AMDA (Automated Multi-Dataset Analysis, http://cdpp-amda.cesr.fr/) developed
by CDPP (http://cdpp.cesr.fr/) and the onset database established by the team of THEMIS
ground base observatory, we try to investigate the relation between auroral substorm
onsets and in-situ electromagnetic wave activity. The relation with the plasma transport,
in both radial and azimuthal directions, will be also addressed.
Wave Propagation and Substorm Timing: Beyond Ideal MHD
Robert L. Lysak(1), Yan Song(1), and Naiguo Lin(2)
(1) School of Physics and Astronomy, University of Minnesota
(2) Space Sciences Laboratory, University of California, Berkeley
THEMIS observations have indicated that wave propagation by ideal MHD waves may
not be fast enough to account for the timing of events during substorms. The question
then arises if non-MHD wave modes or particle propagation could convey information
through the tail during substorms. Kinetic Alfven waves have a faster group velocity than
MHD Alfven waves, but also suffer wave damping. Whistler mode waves can travel
much faster than the Alfven speed for parallel propagation, but not for perpendicular
propagation. In addition, observations of whistler mode waves at sufficient amplitudes to
carry significant amounts of energy have not been observed to our knowledge. Of
course, electrons can travel at speeds much larger than MHD wave speeds, but must
overcome the mirror force to reach the inner magnetosphere to produce the aurora.
Thus, the purpose of this talk is to present the relevant physics behind these mechanisms
with the hopes of inciting discussion of the roles each may play in the substorm process.
Thin Current Sheet in the Substorm Late Growth Phase:
Modelling of THEMIS Observations
Xuzhi Zhou(1)
(1) Institute of Geophysics and Planetary Physics,
University of California, Los Angeles
[NO FORMAL ABSTRACT]
Plasma Sheet Pressure Evolution Associated with
Substorm-Related Activities
X. Xing(1), L.R. Lyons(1), V. Angelopoulos(2), D. Larson(3), J. McFadden(3),
C. Carlson(3), A.Runov(2), K.H. Glassmeier(4), and U. Auster(4)
(1) Department of Atmospheric and Oceanic Science, UCLA, Los Angeles, CA
90095-1567, USA
(2) IGPP/ESS UCLA, Los Angeles, CA 90095-1567, USA
(3) Space Sciences Laboratory, UCB, Berkeley, CA 94720-7450, USA
(4) TUBS, Braunschweig, D-38106, Germany
We investigated the inner plasma sheet plasma pressure evolution associated with
substorm onset in the second THEMIS tail season. Present results support the picture we
proposed from the results of the first tail season that associated with substorm onset, the
plasma sheet pressure earthward of -12 RE generally increases due to the particle
energization. At the same time the pressure tailward of -16 RE show substantial decrease,
which indicate a cross-tail current reduction occurs in that tailward region. However, for
some of our substorm events, a substantial pressure decrease can be observed as
earthward as -11 RE, which implies the cross-tail current reduction extends to the inner
plasma sheet region. The ground data show a trend that the westward electrojet is located
more equatorward when the pressure decrease is found more earthward. The inner edge
of the current reduction region for the cases associated with pressure increase in the inner
plasma sheet is undetermined. Thus the relationship between the auroral break up arc,
which is believed to map to ~-10 RE, and the pressure and current evolution in that
region of the plasma sheet near the time of onset needs more careful discussion.
THEMIS Observations of High-energy Ions in the Central Plasma Sheet
A. Runov(1), V. Angelopoulos(1), X.-Z. Zhou(1), C. T. Russell(1), D. Larson(2),
J. McFadden(2), J. Bonnell(2), K.-H. Glassmeier(3,4), and I. Mann(5)
(1) IGPP UCLA, Los Angeles, CA, USA
(2) SSL UCB, Berkeley, CA, USA
(3) TUBS, Braunschweig, Germany
(4) MPS, Katlenburg-Lindau, Germany
(5) University of Alberta, Edmonton, Alberta, Canada
We present some first results of analysis of THEMIS SST ion measurements in the
central plasma sheet during 2008 and 2009 THEMIS tail-science seasons. The data were
selected according the following criteria: i) |Bx|<15 nT, |B|<15 nT for THB (P1) and
THC (P2) and |Bx|<40, |B|<40 for THD (P3), THE (P4), and THA (P5) to select central
plasma sheet samples, and ii) 00:20<UT<12:20 to select the fast survey mode data and
North-America conjunctions. The data from 4th, 5th, and 6th SST energy channels (100 200 keV) were used for the statistical analysis. We examine a dependence of the
differential particle flux J [p+/cm2/s/sr/keV] on geomagnetic activity, spatial distributions
of the flux, its azimuthal anisotropy, energy distributions, and temporal variations at
different regions in the magnetotail plasma sheet.
Flow, Aurora and Pi2 Associations Observed by THEMIS
L. Kepko(1), E. Spanswick(2), E. Donovan(2), V. Angelopolous(3),
J. McFadden(4), C. Carlson(4), K.-H. Glassmeier(5), and H. Singer(6)
(1) University of New Hampshire, Space Science Center, Durham, NH, USA
(2) University of Calgary, Canada
(3) UCLA, Los Angeles, CA, USA
(4) Space Sciences Laboratory, University of California, Berkeley, CA, USA
(5) TUBS, Braunschweig, Germany
(6) NOAA/Space Weather Prediction Center, Boulder, CO, USA
It has been known for decades that auroral substorm onset occurs on (or at least near) the
most equatorward auroral arc, which is thought to map to the near geosynchronous
region. The lack of auroral signatures poleward of this arc prior to onset has been a major
criticism of flow-burst driven models of magnetospheric activity. I present an event from
2008 using multi-spectral all sky imager data from Gillam and in-situ data from
THEMIS. The multispectral data indicate an equatorward moving auroral form prior to
substorm onset. When this form reaches the most equatorward arc, the arc brightens and
an auroral substorm begins. The THEMIS data show fast Earthward flows prior to onset
as well. I suggest that the results strongly support flow-burst driven models of
magnetospheric activity.
An Attempt to Shed Further Light on Auroral Spirals Using
Ground-Space Observations from THEMIS
A. Keiling(1), V. Angelopoulos(1), S. Mende(1), J. McFadden(1), D. Larson(1),
E. Donovan(2), J. Weygand(3), K.-H. Glassmeier(4), H.U. Auster(4), and O. Amm(5)
(1) Space Sciences Laboratory, UCB, Berkeley, CA, USA
(2) Department of Physics and Astronomy, University of Calgary,
Calgary, Alberta, Canada.
(3) IGPP, UCLA, Los Angeles, CA, U.S.A.
(4) TUBS, Braunschweig, Germany
(5) Finish Meteorological Institute, Helsinki, Finland
The auroral spiral, occurring in some auroral arcs, is a prominent vortex structure in the
optical data. Although ample ground-based observational descriptions of auroral spirals
exist, their magnetospheric counterparts are far less investigated. In particular, no
conjugate comparison of auroral spirals and their generator region in near-Earth plasma
sheet exist (to our knowledge). Thus, many questions remain regarding the generation
mechanism of auroral spirals. Here, we attempt to shed further light on auroral spirals
using conjugate ground-space observations from THEMIS's ground observatories and
satellites during the formation of auroral spirals.
Finding the Isotropic Boundary
C. Gabrielse(1), V. Angelopoulos(1), J. McFadden(2), D.E. Larson(2),
and M. Kubyshkina(3)
(1) IGPP/UCLA, Los Angeles, CA
(2) SSL, UC Berkeley, Berkeley, CA
(3) University of St. Petersburg, St. Petersburg, Russia
With the launch of THEMIS and its time spent in the tail season, the question of insideout or outside-in has been studied by several papers. (Angelopoulos, et al., Science, 2008;
Runov et al., JGR, 2008; Gabrielse et al., JGR, 2008.) An important question at hand is:
can the information really travel as fast as the results imply, and can the reconnection site
truly be closer than 20 Re? By determining the radius of curvature of the field lines at the
neutralsheet downtail, we can use the kappa-squared value (radius of curvature/particle
gyro-radius ~8) to determine the physical location of the isotropic boundary. Mapping
this back to the ionosphere at the same location that we see the visible aurora would
affirm the interpretations of the outside-in papers.
Global Alfvenic Interaction and Substorm Onset
Yan Song(1), and Robert L. Lysak(1)
(1) School of Physics and Astronomy, University of Minnesota
We suggest that substorm onset is the result of Alfvenic interactions in the global current
system including the tail and magnetopause current sheets as well as the auroral fieldaligned current system. During the growth phase, Alfvenic interaction between the solar
wind and magnetosphere occurs in multiple localized regions throughout the
magnetopause current sheets and stresses the tail current sheet, leaving it susceptible to
further dynamical processes that often involve the generation of MHD waves and the
wave mode conversion. The decrease of momentum transfer from the solar wind into the
magnetosphere due to changes in solar wind parameters leads to a force imbalance in the
whole magnetotail and the generation of fast mode waves and plasma flows. These waves
interact with the stressed current sheet and cause the breakdown of the frozen-in
condition and the perturbations of fields and flows in multiple localized regions
throughout the tail current sheet. During these processes and during the further
reconfiguration of the plasma sheet, Alfven waves carrying field aligned currents can be
generated which lead to the subsequent auroral development seen in the expansion phase.
Substorm auroral generation is also a result of the Alfvenic interaction in the global M-I
coupling system. Unlike previous models, where substorm onset is assumed to be the
result of a simple causal chain of events, this alternative Alfvenic interaction scenario
suggests the substorm onset results from coupled physical processes in a driven system
that may follow a more complicated temporal sequence.
FAST Observations of Field-Aligned Currents over
the THEMIS Ground Station Array
Robert J. Strangeway(1)
(1) Institute of Geophysics and Planetary Physics,
University of California, Los Angeles, CA 90095
In 2008 the FAST spacecraft had is apogee in the northern hemisphere in March through
May and September through November. We have begun an analysis of FAST
observations when the spacecraft was over the THEMIS ground station array. FAST
observes the signatures of inverted-V and Alfven-wave accelerated electrons, as well as
the magnetic field perturbations of the associated field-aligned currents. We will compare
these observations with the THEMIS all sky imagers and ground magnetometers.
Statistical Analysis of the Response of the Inner Magnetospheric
Magnetic Field and Plasma Perturbation to Substorm Expansions
Tung-Shin Hsu(1), Robert L. McPherron(1), Vassilis Angelopoulos(1),
Margaret Kivelson(1), and the THEMIS Team
(1) Institute of Geophysics and Planetary Physics, University of California
Los Angeles, Los Angeles, CA 90095-1567, USA
It is generally accepted that the synchronous magnetic field becomes more tail-like
during the growth phase and more dipole-like during the expansion phase of
magnetospheric substorms. The cause of the substorm onset is still one of the central
issues of current magnetospheric studies. There are several models trying to explain
substorm. The near the near-earth neutral line (NENL) model suggests that reconnection
is the trigger of substorm onset. In this model, the plasma flow caused by reconnection
brake in the near earth region and thus cause flux pile-up. However, it has been claimed
that the detection of a fast flow in the magnetotail is not always followed by ground
substorm activity. In this study we examine a number of substorms from the THEMIS tail
passage for which we have detailed information about the time history of activity.
Detailed timing relationship between plasma flows, geosynchronous local onsets, Pi 2
pulsation at different locations will be examined as well as their occurrence frequency at
substorm onsets. The understanding of the occurrence frequency and relative timing can
help us understand the evolution of substorms.
THEMIS Multi-Point Observations of Traveling Compression
Regions: First Tail Season Results
S.M. Imber(1), and J.A. Slavin(1)
(1) NASA Goddard Space Flight Center, Greenbelt, MD, USA
The first tail season of the THEMIS mission provides rare opportunities for observations
of travelling compression region (TCR) development and transport at multiple points in
the Earth's magnetotail. Using the two most distant THEMIS satellites, examples are
presented of not only TCR motion, but also the rapid formation and disappearance of
TCRs on time scales of minutes. The implications of these new, multi-point
measurements for the formation of new X-lines and secondary flux rope development and
possibly the coalescence of smaller flux ropes in larger ones will be discussed.
Characterizing the ULF Power Spectra during
the Substorm Expansion Phase
Kyle R. Murphy(1), I. Jonathan Rae(1), Ian R. Mann(1)
(1) University of Alberta, Department of Physics, Canada
Impulsive Ultra low frequency (ULF) waves are observed during magnetic substorms in
the Pi1 and Pi2 bands with periods of 1-40s and 40-150s respectively, as first classified
by Jacobs et al. 1964. Recent work on substorm timing utilizing ground-based
observations of the development of small scale auroral features and ULF waves has
shown that waves with periods between ~16-96s, spanning both the Pi1 and Pi2 period
band, play an important role in identifying the initial expansion of magnetic substorms in
the ionosphere. Understanding whether differences or similarities exist between long
period Pi1s, and waves in the classical Pi2 band is important for understanding the
physical processes generating these pulsations and the coupling of the ionosphere and
magnetosphere during magnetic substorms. Historically, onset Pi2s have been associated
with the formation of the substorm current wedge during the substorm expansion phase,
while the longer period Pi1 pulsations have been recently associated with the initial
seconds of substorm onset and the brightening of the onset arc. By statistically
characterizing the spatial distribution of ULF power with respect to substorm onset
locations identified by the IMAGE satellite in the Frey et al. database, we examine
whether the different Pi1 and Pi2 bands of ULF waves observed at substorm onset are
physically disparate phenomena, or whether the historical classification of ULF waves
observed during magnetic substorms is in need of revision. In particular we seek to
establish whether Pi1 and Pi2 are both generated by the same physical process, and
whether the Jacobs et al. classification remains appropriate for distinguishing between
onset ULF waves.
The Interrelationship of Auroral Onset, Dipolarization,
Fast Flow, and Injection
Emma Spanswick(1), Eric Donovan(1), Vadim Uritsky(1), Jun Liang(1),
Brian Jackel(1), and Stephen Mende(2)
(1) University of Calgary, Canada
(2) University of California, Berkeley, CA, USA
Using a variety of ground-based instruments/techniques we are now able to quantify the
location of certain magnetospheric boundaries and phenomena. These include: (1) the
equatorward boundary of the proton aurora (428nm), which is believed to represent the
inner edge of a strong pitch angle scattering region determined by the magnetic topology.
Across this boundary the magnetic field changes from a tail-like to dipolar-like, (2) The
poleward edge of the 630nm (redline) aurora which is believed to correspond to the
ionospheric footprint of the open-closed field line boundary, and (3) sudden rises in
riometer absorption that have been connected to the onset of dispersionless injection at a
given location. Using the THEMIS-ASI array, the NORSTAR Multispectral ASI array,
the CGSM photometers and riometers we place the auroral breakup and onset of
dispersionless injection relative to these magnetospheric locations. In this paper, we
combine information provided by these ground-based arrays with the THEMIS satellite
data in an effort to elucidate the relationship between aurora breakup, dispersionless
injection, dipolarization and magnetospheric fast flow.
Observations of Electron Energization in the Vicinity of an
X-line in the Magnetotail on 2009-02-07
Marit Oieroset(1), Tai Phan(1)*, Jonathan Eastwood(1),
Vassilis Angelopoulos(2), Davin Larson(1), Jim McFadden(1),
John Bonnell(1), Forrest Mozer(1), and Karl-Heinz Glassmeier(3)
(1) SSL, University of California, Berkeley, CA, USA
(2) IGPP, University of California, Los Angeles, CA, USA
(3) IGEP, TU Braunschweig and MPS, Katlenburg-Lindau, Germany
We present the burst-mode observations of particles and fields during an X-line crossing
by THEMIS-B in the magnetotail on February 7, 2009. In addition to the classic Hall
signatures the spacecraft detected enhancements of energetic electrons in the vicinity of
the X-line crossing. We will discuss the electron energization in relation to magnetic
islands and to the X-line.
THEMIS Observation of Waves and Wave-Particle
Interactions in the Neutral Sheet
X.H. Deng(1), M. Ashour-Abdalla(1), M. Zhou(1), D. Schriver(1),
and M. El-Alaoui(1)
(1) IGPP-UCLA, 405 Hilgard Ave., Los Angeles, CA 90095 USA
In this talk we will present initial results of THEMIS observations on waves and wave
particle interactions observed in the magnetotail neutral that may be associated with
reconnection. The 3 dimensional (3D) electric and magnetic field observations with high
time resolution waveform data provide an unprecedented opportunity for this study
during the THEMIS tail science campaign. Several electromagnetic waves and
electrostatic waves have been found near the neutral sheet and plasma boundary during
the events with plasma flow reversal. We will discuss the characteristics of waves and
particles, and the 3D structure of nonlinear solitary waves and their possible role in
reconnection.
Events list: Feb. 26, 2008, Jan. 26, 2009, Feb. 07, 2009, Feb. 15, 2009, Feb. 23, 2009
Analysis of Substorms During the Second Tail Season
V. Angelopoulos(1), A. Runov(1), X. Z. Zhou(1), S. Frey(2), J. McFadden(2),
D. Larson(2), S. Mende(2), H. Frey(2), J. Bonnell(2), U. Auster(3), K. H. Glassmeier(3),
O. LeContel(4) and A. Roux(4)
(1) Institute of Geophysics and Planetary Physics, University of
California, Los Angeles, California, USA
(2) Space Sciences Laboratory, University of California, Berkeley,
California, USA
(3) IGEP, TU Braunschweig and MPS, Katlenburg-Lindau, Germany
(4) Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau,
France
During the second tail season the P1, P2 orbits were redesigned to reside closer to the
neutral sheet in order to capture reconnection events in the midtail and correlate the
particle signatures with substorm onset. We review the substorms that have been
observed thus far and perform timing analysis on two of them: Major conjunctions of
January 26th and Feb 15th, 2009. Due to the low solar and geomagnetic activity in the
first half of 2009, the substorms encountered were localized and often the ionospheric
conductivity was low enough that magnetic signatures are small or absent. This presents
the opportunity to compare small with large substorms from multiple vantage points in
the tail. Based on ACE and STEREO correlations, it is expected that Feb 23rd will be an
active time, high quality conjunction. The extra benefit from Cluster placement in that
event will also be discussed. Preliminary results show that small substorms and high
latitude substorms have all features of injections, fast flows dipolarizations and
reconnection that are found in larger substorms, but are more confined in their local time
extent on the ground and seemingly also in the magnetosphere.
Multiscale Dynamics of Optical Aurora Associated
with Near-Earth Substorm Breakup
Vadim Uritsky(1), Eric Donovan(1), Emma Spanswick(1), Jun Liang(1),
Brian Jackel(1), and Stephen Mende(2)
(1) University of Calgary, Calgary, Alberta, Canada
(2) University of California, Berkeley, California, USA
The network of ground-based all-sky imagers is a valuable component of the
international THEMIS mission providing an unprecedented opportunity of studying
complex types of auroral disturbances associated with the substorm onset. In this talk, we
show that the substorm onset is accompanied by a significant enhancement of spatial and
temporal coherenceof the growth phase aurora prior to the main breakup. The precursory
buildup of the multiscale auroral complexity can be seen in statistical indices obtained
from the higher-order structure function analysis of optical auroral fluctuations. This
process is accompanied by increased electric field fluctuations in the tail as seen by in
situ THEMIS probes indicating a possible formation of a thin electron current sheet. The
analysis of time evolution of azimuthal arc profiles reveals various forms of plasma
motion including broad-band turbulence localized irregular intensifications, as well
westward propagating structures with traveling speeds of 2.0 - 5.0 km/s accompanied by
in situ signatures of flapping oscillations in the magnetotail. The post-breakup auroral
dynamics exhibits another type of wave-like structures which typically travel from dawn
to dusk at the velocity 8.0 - 12.0 km/s, recurrence time 20 - 40 s. These waves first appear
within a local MLT sector (~1 hour MLT) shortly before to the global expansion onset.
We argue that the observed signatures can carry a critical piece of evidence regarding the
kinetic nature of the initial magnetotail instability controlling the late growth and the
early expansions stages of the magnetospheric substorm. Due to the broad range of scales
involved, and due to the fact that this range is inherently spatiotemporal, the observed
signatures can be seen in high-resolution optical auroral data and are not detectable from
in situ observations alone.
THEMIS Substorm Science in the Second Tail Season: Near-Earth
Magnetosphere-Ionosphere Coupling Event Selection and Analysis
I.J. Rae(1), I.R. Mann(1), K.R. Murphy(1), D.K. Milling(1),
D. Sibeck (2), and V. Angelopoulos (3)
(1) Department of Physics, University of Alberta, Edmonton, Alberta, Canada
(2) NASA Goddard Space Flight Center, USA
(3) University of California at Los Angeles, CA, USA
During conjunctions to the Canadian sector, the THEMIS satellites provide a unique
window for establishing the relationship between disturbances at the probes and the time
sequence of magnetic Pi1 and small scale auroral arc development in the ionosphere. We
present a preliminary assessment of the ground-based magnetic bays, Pi1, low resolution
auroral arc brigthenings, and in-situ GOES dipolarizations before and after a number of
major and minor probe conjunctions to the GBO array during the second tail season. We
will identify a number of events with promising features in terms of examining and
understanding the near-Earth relationship between in-situ measurements and those in the
ionosphere, including potential rapid coupling between the equatorial plane and the
ionosphere (e.g., Rae et al., 2009; Angelopoulos et al., Science, 2008). We propose to
select events which focus on addressing the near-Earth plasma evolution and related M-I
coupling, rather than trying to distinguish between "inside to out" or "outside to in
scenarios" - however the output from the event studies will contribute towards that goal.
We propose to identify events and analysis leads and advance case studies using data
analysis completed by workshop participants; we hope that this can begin in real-time
during the workshop.
Propagation Velocity of Near-Earth Dipolarization
S. Li(1), V. Angelopoulos(1), A. Runov(1), X.Z. Zhou(1), J. McFadden(2), D. Larson(2),
J. Bonnell(2), U. Auster(3), K. H. Glassmeier(3), O. Le Contel(4), and A. Roux(4)
(1) Institute of Geophysics and Planetary Physics, University of California, Los Angeles,
California, USA
(2) Space Sciences Laboratory, University of California, Berkeley, California, USA
(3) Institut fur Geophysik und Extraterrestrische Physik, Technische Universitat,
Braunschweig, Germany
(4) Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau, France
We have studied signatures of negative-then-positive excursion of the northward
magnetic field using several near-Earth THEMIS satellite conjunctions in mid/late
March, 2008. The objective is to quantify the propagation speed of the dipolarization and
compare it with the measured flow velocity, in order to determine the means/mode of
propagation of the dipolarization. We focused on the subset of dipolarizations that exhibit
a bipolar signature because this signature is evidence of being closest to the central
meridian of the substorm onset. Such signatures are observed at the very beginning of the
substorm dipolarization. Comparing the velocity calculated using the time delay between
different satellites and the flow velocity taken by the ESA instrument, we find that the
propagation velocity of the structure was faster than the flow velocity. The deviation of
the propagation speed from the convective flow exhibits no relation to plasma
parameters, e.g., the magnitude of the flow velocity itself. This suggests that either the
depolarization represents most often an East-West expansion of the activity, or that the
propagation fronts are waves decoupled from the convective flow.
Significance of Weak Activities in Magnetospheric Substorm Research
C.-I. Meng(1*), and A. T. Y. Lui(1)
(1) JHU/APL, USA
(1*) Ret. from JHU/APL, USA
In several past studies of magnetospheric activities related to substorms, weak signatures
in auroral indices or magnetotail activities are cast as insignificant and excluded as
substorm activities by labeling them as pseudo-breakups. In this presentation, we discuss
several features of these activities that are no less significant than those from large
substorm disturbances. We point out that investigations of these weak activities have the
benefit that secondary processes from the primary process for substorms are likely
absent, thus allowing better identification of the primary substorm process.
Large-scale Plasma Sheet Oscillation and Relation
to Substorms: THEMIS Case Study
Y.S. Ge(1), J. Raeder(1), and L. Kepko(1)
(1) University of New Hampshire, Durham, New Hampshire, USA
In the second tail season of THEMIS mission, the inclination angle of middle-tail
spacecraft (P1 and P2) is smaller than that in the first tail season, which enables us to
investigate the dynamics of central plasma sheet during substorms. On February 15,
2009, large-scale oscillations in the plasma sheet are found on the inner spacecaft (P3, P4
and P5) following a moderate substorm, which is also followed by a strong substorm with
multiple onsets. Strong tailward and earthward flows are respectively observed by P1 and
P2 at the first substorm, suggesting that tail reconnection occurs between two spacecraft.
Multiple flow bursts with corresponding multiple dipolarizations following the first
substorm are found on P1 while P5 observes large-scale plasma sheet oscillations. During
the following second substorm, however, no strong flow is observed. The oscillations
of plasma sheet seen on the inner spacecraft have a time-scale of 20-30 minutes. The
ground all-sky images also show multiple arcs during the time of these oscillations. In
this study, we use THEMIS observations to investigate the possible relation of substorm
onsets with these oscillations of tail plasma sheet.
Observations of Double Layers in Earth’s Central Plasma Sheet
R.E. Ergun(1,2), L. Andersson(2), J. Tao(1,2), V. Angelopoulos(3), J.W. Bonnell(4),
J.P. McFadden(4), D.E. Larson(4), S. Eriksson(2), T. Johansson(2), C.M. Cully(5),
D.N. Newman(6), M.V. Goldman(6), A. Roux(7), and O. Le Contel(7),
W. Baumjohann(8), and K.-H. Glassmeier(9)
(1) Department of Astrophysical and Planetary Sciences, University of Colorado,
Boulder, Colorado, USA
(2) LASP, University of Colorado, Boulder, Colorado, USA
(3) IGPP, University of California, Los Angeles, California, USA
(4) SSL, University of California, Berkeley, California, USA
(5) Swedish Institute of Space Physics, Uppsala, Sweden
(6) Center for Integrated Plasma Studies, University of Colorado,
Boulder, Colorado, USA
(7) LPP, CNRS/Ecole Polytechnique/UPMC, France
(8) Space Research Institute, Austrian Academy of Sciences, Graz, Austria
(9) Institut für Geophysik und Extraterrestrische Physik, Technische Universität,
Braunschweig, Germany
We report the first direct observations of parallel electric fields carried by double layers
(DLs) in the central plasma sheet of the Earth’s magnetosphere. The observations are
made by the THEMIS spacecraft. The DLs have a parallel electric field signal that is
analogous to that reported by the FAST satellite in the auroral acceleration region which
has been verified by numerical sim-ulations. The most interesting of the observations is a
series of five or more DLs made by the THEMIS D spacecraft at ~10 earth radii (RE)
during a bursty bulk flow event. DLs also are observed in the current sheet and plasma
sheet boundary layer, all during magnetically active times. These observations imply that
strongly nonlinear and kinetic behavior is intrinsic to the Earth’s plasma sheet.
SESSION D (8/11)
Lowest Intensity of Radiation Belt Electrons
Measured by THEMIS and other Spacecraft during Jan-Feb of 2009
Xinlin Li(1) et al.
(1) LASP, University of Colorado, Boulder, Colorado, USA
[NO FORMAL ABSTRACT]
Drift Mirror Waves Observed by THEMIS
in the Duskside Magnetosphere
O.D. Constantinescu(1,2), K.-H. Glassmeier(1), F. Plaschke(1), U. Auster(1),
V. Angelopoulos(3), W. Baumjohann(4), K.-H. Fornacon(1), E. Georgescu(5),
W. Magnes(4), J.P. McFadden(3), R. Nakamura(4), and Y. Narita(1)
(1) Institute for Geophysics and Extraterrestrial Physics,
Technical University of Braunschweig, Germany
(2) Institute for Space Sciences, Romania
(3) Space Sciences Laboratory, University of California, USA
(4) Space Research Institute, Austrian Academy of Sciences, Austria
(5) Max Planck Institute for Solar System Research, Germany
We present a statistical study of THEMIS observations of compressional ULF waves in
the outer equatorial dusk side magnetosphere. The observed events occur inside a well
defined spatial domain in the outer equatorial dusk side magnetosphere. We analyze these
waves using the unique string of pearls configuration of the THEMIS constellation to
evaluate their phase speed and propagation direction. We find that the waves are
propagating sunward (westward) and radially outwards, orthogonal to the mean magnetic
field, with phase speeds ~30 km/s and higher in the spacecraft frame. In the plasma frame
the propagation direction is still sunward, with lower speeds (up to 30 km/s for most
events). The oscillations exhibit a strong anti-correlation between the magnetic field and
the plasma density. Based on this, as well as on their low propagation speed, orthogonal
to the mean magnetic field propagation direction and almost parallel to the magnetic field
maximum variance direction, we conclude that the most likely source of these waves is
the drift mirror mode.
Statistical Analysis of the Global Distribution of Chorus Waves
and Suprathermal Electrons Observed on the THEMIS Spacecraft
W. Li(1), R.M. Thorne(1), V. Angelopoulos(2), J. Bortnik(1), C.M. Cully(3),
B. Ni(1), O. Le Contel(4), A. Roux(4), J.P. McFadden(5), C.W. Carlson(5),
U. Auster(6), and W. Magnes(7)
(1) Department of Atmospheric and Oceanic Sciences, University of California,
Los Angeles, 405 Hilgard Avenue, Los Angeles, CA, 90095-1565, USA.
(2) IGPP/ESS University of California, Los Angeles, CA, 90095-1567, USA.
(3) Swedish Institute of Space Physics, Box 537, SE-751 21, Uppsala, Sweden.
(4) Centre d'Etude des Environnements Terrestre et Planétaires (CETP),
10-12 Avenue de l’Europe, 78140 Vélizy, France.
(5) Space Sciences Laboratory, University of California, Berkeley,
7 Gauss Way, Berkeley, CA, 94720-7450, USA.
(6) Institut für Geophysik und extraterrestrische Physik der Technischen
Universität Braunschweig, Mendelssohnstrasse 3, 38106, Braunschweig,
Germany.
(7) Space Research Institute, Austrian Academy of Sciences,
Schmiedlstrasse 6, 8042 Graz, Austria.
Magnetic field filter bank data from the THEMIS spacecraft, with 5 probes in nearequatorial orbits, are used to study the global distribution of chorus waves. Our results
confirm the earlier CRRES analysis of the strong dependence of wave amplitudes on
geomagnetic activity, and the confinement of nightside emission to low magnetic
latitudes. An important new finding from THEMIS is the much stronger occurrence of
chorus in the pre-noon sector at L>7, a region not sampled by CRRES. Moderate dayside
chorus is present >10% of the time and can persist even during periods of low
geomagnetic activity. In addition, a statistical analysis is also performed to provide the
global distribution of suprathermal electrons (flux and anisotropy) using ESA data in
order to explain the typical features of chorus distribution.
Simulation of EMIC Excitation in a Model Magnetosphere Including
Structured High-Density Plumes
Lunjin Chen(1), Richard Thorne(1), and Richard Horne(2)
(1) Department of Atmospheric and Oceanic Sciences,
University of California, Los Angeles, USA
(2) British Antarctic Survey, Natural Environment Research Council,
Cambridge, England
The HOTRAY code is used to evaluate the path integrated gain of EMIC waves as a
function of frequency in two propagation bands above the O+ and He+ gyrofrequencies.
Calculations are performed over a range of L-shell (3<L<7) assuming a cold H+ - He+ O+ plasma with an additional bi-Maxwellian hot ring current proton distribution. The
cold plasma model includes a plasmasphere and high-density storm-time plume region
containing spatial density fluctuations. Strongest wave gain (>40 dB) is found near the
plasmapause, within regions with density structure in the plume, and in the low density
trough at L>=7. As a self-consistent test on whether EMIC waves play an important role
in relativistic electrons loss from the radiation belts, the minimum cyclotron resonant
electron energy is evaluated as a function of wave frequency and L shell for those EMIC
waves that exhibit significant gain. The lowest electrons resonant energies (~few MeV)
are found in structured plumes. The sensitivity of the wave gain and electron minimum
resonant energy to variation in thermal ion compositions, the energetic proton properties,
or plume density structure are also investigated. The simulation results can be tested
against THEMIS data in the future.
Statistical Study of Pc4 and Pc5 Pulsations in the Inner
Magnetosphere as Measured by THEMIS
W. Liu(1), T.E. Sarris(1), X. Li(1), S.R. Elkington(1),
R. Ergun(1), V. Angelopoulos(2), J. Bonnell(3), K.-H. Glassmeier(4),
and U. Auster(4)
(1) Lab. for Atmospheric and Space Physics, Univ. of Colorado,
Boulder, Colorado
(2) IGPP, University of California-Los Angeles, California
(3) Space Sciences Lab, University of California-Berkeley, California
(4) IGEP, Technical University of Braunschweig, Germany
The Ultra Low Frequency (ULF) waves in the Pc4 and Pc5 bands are ubiquitous in the
inner magnetosphere and have significant influence on energetic particle transport.
Investigating the source of ULF waves also helps us better understand the interaction
processes between the solar wind and the magnetosphere. However, due to the limitation
of the instrumentation and the spacecraft orbit, the complete local time and L-shell
distribution of the ULF waves in the inner magnetosphere has not been studied. The
recent THEMIS mission provides unique opportunities to investigate the spatial
distribution of ULF pulsations across different L-shells with full local time coverage in
the inner magnetosphere, with both electric and magnetic field measurements. In this
study, Pc4 and Pc5 pulsations in the electric field observations are identified throughout
13 months of measurements, covering 24 hours in local time. The pulsations are
characterized as either toroidal or poloidal (including compressional) mode depending on
the polarization of the electric field. Subsequently, their occurrence rate and wave power
distributions in radial distance and local time are recorded. While the distributions of both
Pc4 and Pc5 events vary greatly with radial distance and local time, Pc4 events are more
frequently observed in the inner region around 5-6 RE and Pc5 events are more
frequently observed in the outer region around 7-9 RE, which suggest that the
fundamental mode of the field line resonance (FLR) is an important source of the ULF
waves. Both Pc4 and Pc5 toroidal modes are mostly observed along the flank sides,
which suggest that both Pc4 and Pc5 toroidal modes are likely associated with the K-H
instability. These observations are also an excellent source for the parameterization of
models that require ULF wave power as input in order to provide estimation of radial
diffusion rates of energetic particles in the inner magnetosphere.
Inner Magnetospheric THEMIS Science at the Plasmapause:
Operational Configurations for Science Closure?
I.R. Mann(1), M. Usanova(1), I.J. Rae(1), K. Murphy(1),
J.W. Bonnell(2), D. Sibeck(3), and V. Angelopoulos(4)
(1) Department of Physics, University of Alberta, Edmonton, AB.
(2) University of California, Berkeley, CA, USA.
(3) NASA Goddard Space Flight Centre, USA.
(4) University of California at Los Angeles, CA, USA
The THEMIS satellites provide a unique window for examining inner magnetospheric
science close to the plasmapause. Science targets include the role of the plasmapause in
EMIC wave excitation, important since multi-point equatorial observations of EMIC
wave excitation have never before been possible, and these EMIC waves are believed to
play a key role in energetic wave-particle coupling in the ring current and radiation belts.
During the cruise phase, THEMIS provided excellent data in the plasmapause region
including EMIC waves driven in the inner magnetosphere during solar wind compression
(e.g., Usanova et al., GRL, 2008), however, following the beginning of the prime mission
data has in general not been collected below L<6. There are numerous (~30) subsequent
examples of inner magnetosphere EMIC waves we have observed on the ground during
solar wind compressions during the prime mission, but none have THEMIS satellite
coverage close to the plasmapause. We propose a discussion during the workshop to
discuss rectifying this for the remainder of the prime and extended mission on the
THEMIS probes. This discussion should include the potential of adding continuous data
coverage for lower-L for at least FGM and EFW SC potential, additional standard mode
operations into at least L=<3 especially during conjunctions with the north American
sector, and targeted burst modes of high resolution measurements close to the
plasmapause. Significantly, burst mode operations could be valuable if triggered close to
the plasmapause. This could include potential burst mode triggering on options which
include: i) on fixed L ranges spanning nominal plasmapause during in-bound and outbound Canadian magnetic conjuctions; ii) using a model plasmapause location driven by
real-time Kp or other index history; or iii) triggered for a specified period on-board
automatically when large gradients in spacecraft potential are observed.
A Case Study of Radial Transport of Energetic Electrons in the Inner
Magnetosphere based on THEMIS and other Satellite Measurements
Weichao Tu(1), Xinlin Li(1), and Scot Elkington(1)
(1) LASP, University of Colorado, Boulder
There has been increasing evidence that ULF waves play a fundamental role in the
dynamics of energetic electrons in the inner magnetosphere. In this work we perform a
case study on the radial transport of energetic electrons in the radiation belt by analyzing
the solar wind data, geomagnetic activity, ULF waves and energetic particle
measurements from THEMIS and GOES, etc. associated with this event. MHD
simulation is also performed for this event and preliminary MHD results on the global
ULF oscillations will be shown in the work if ready.
Generation of EMIC Waves in the Inner Dayside Magnetosphere
during Magnetospheric Compressions
M.E. Usanova(1), I.R. Mann(1), I.J. Rae(1), Z.C. Kale(1), A. Parent(1),
V. Angelopoulos(2), J.W. Bonnell(3), K.-H. Glassmeier(4), U. Auster(4),
M. Sandanger(5), F. Soraas(5), and H.J. Singer(6)
(1) Department of Physics, University of Alberta, Edmonton, Alberta, Canada
(2) University of California at Los Angeles, CA, USA
(3) Space Sciences Laboratory, University of California, Berkeley, California, USA
(4) Institut fur Geophysik und Extraterrestrische Physik, Technische
Universitat Braunschweig, Braunschweig, Germany
(5) University of Bergen, Bergen, Norway
(6) NOAA Space Weather Prediction Center, Boulder, Colorado, USA
Electromagnetic ion cyclotron (EMIC) waves are believed to play a significant role in the
dynamics of energetic particles in the inner magnetosphere, both keV protons and MeV
electrons, causing them to precipitate into the ionosphere via resonant interaction. In
order to incorporate the EMIC-related loss processes into global magnetospheric models
one needs to know solar wind and magnetospheric conditions favorable for EMIC wave
excitation as well as localization of the waves in the magnetosphere. In this work, we
investigate the role of magnetospheric compression in the generation of EMIC waves.
While compression-related EMIC waves were previously found to be common for the
outer dayside magnetosphere, there has been little experimental evidence for the wave
generation during compressions in the inner magnetosphere. Theoretical studies have
shown that in the inner magnetosphere resonant interaction with EMIC waves may be
important for MeV electron loss from the radiation belts, especially in regions of high
plasma density and low magnetic field, e.g., outer regions of quiet-time plasmasphere.
We will present multiple examples of EMIC wave generation during the dayside
magnetospheric compressions originating from enhanced solar wind densities and
simultaneous observations of energetic proton precipitation into the ionosphere. Such
precipitations were previously found to be co-located with those of relativistic electrons.
Based on our observations, we will discuss the following possibility for the inner
magnetosphere loss processes: enhancements in solar wind density -> magnetospheric
compression -> generation of EMIC waves in regions of high plasma density ->
consequent loss of energetic particles and address the question of how this hypothesis can
be tested using THEMIS instrumentation.
SESSION X (Part of SESSIONS A and B)
Understanding Kepler's Laws Using Orbit Animation of
THEMIS Spacecraft
Manju Prakash(1,2), Laura Peticolas(3)
(1) Wilbraham and Monson Academy, Wilbraham, MA 01095
(2) Institute of Geophysics and Planetary Physics & Department of Earth and
Space Sciences, UCLA, Los Angeles, CA 90095
(3) Space Sciences Laboratory, Berkeley, CA 94720-7450
In order to engage and motivate high school students to learn Kepler's laws in mechanics,
I have designed a lesson plan using the website: sscweb.gsfc.nasa.gov/tipsod/. On this
website, students have access to the orbits of SOHO, Cluster, and THEMIS spacecraft.
Students can select orbits of the one of the THEMIS spacecraft (say THEMIS B). They
familiarize themselves with various icons such as axes, planes of the orbits, and speed of
recording data. They learn how to rotate and translate co-ordinate systems and to
introduce the Sun and components of the Earth's magnetosphere. Students measure the
semi-major axis (a) of the elliptical orbit of the spacecraft B. They also record the time
(T) it takes for the spacecraft to complete its orbit around the Earth. Students also learn
the concept of aphelion and perihelion and their relation to major axis of the ellipse. They
use following websites to refine their understanding of the eccentricity of the orbits:
www.powerhouseanimation.com?PRG?EART037.swf,
www.mathwarehouse.com/ellipse/eccentriicty-orbiting-planets.php.
Students repeat above steps for THEMIS A and THEMIS C spacecraft, and verify
Kepler's third law, T2 is proportional to a3. The animation based approach can
significantly enhance student interest and understanding of Kepler's laws. Results on
student participation and their learning experiences along with a brief update on THEMIS
outreach and educational activities will be given.
AMDA, Automated Multi-Dataset Analysis: A Web-Based Service
Provided by the CDPP Usable for THEMIS Data Exploitation
C. Jacquey(1), O. LeContel(2), V. Genot(1), E. Budnik(3), L. Brousillou(1),
R. Hitier(4), M. Bouchemit(1), M. Gangloff(1), A. Fedorov(1), B. Cecconi(5),
N. André(1), B. Lavraud(1), C. Harvey(1), F. Dériot(6), D. Heulet(6),
E. Pallier(1), E. Penou(1), J.L. Pinçon(7). V. Angelopoulos(8), U. Auster(9),
and J. McFadden(10)
(1) CDPP/CESR, CNRS/Université Paul Sabatier, 9, avenue du colonel
Roche, 31028 Toulouse, France
(2) Laboratoire de Physique des Plasmas (LPP), Vélizy, France
(3) Noveltis, Toulouse, France
(4) Co-Libri, Cremefer 11290 Montreal, France
(5) LESIA, Observatoire de Paris-Meudon, 5, place Janssen, 92195 Meudon,
France
(6) CNES, Toulouse, France
(7) LPCE, Orleans, France
(8) Department of Earth and Space Sciences, University of California,
Los Angeles, USA
(9) Technical University of Braunschweig, Germany
(10) SSL, University of California, Berkeley, USA
AMDA (Automated Multi-Dataset Analysis, http://cdpp-amda.cesr.fr/) is a new service
recently opened at CDPP (http://cdpp.cesr.fr/). It is a web-based facility for on-line
analysis of space physics data from either its local database or distant ones. The mirror
THEMIS database at CESR is one of them. The tool allows the user to perform on-line
classical manipulations such as data extraction, data visualization or parameter
computation. AMDA also offers more innovative functionalities such as event search on
the content of the data in either a visual or an automated way. These functionalities
extend to automatic recognition of specific multi-parameter signatures. The AMDA
search tools can be used to perform classification of events and to generate time-tables
and catalogues. Some applications of AMDA to THEMIS data will be presented.
*Presenter