A review of multiple-onset substorm studies enlightened by
Prof. Russell
Ching-Chang Cheng
Department of Electronic Engineering, National Formosa University, Hu-Wei, Taiwan
Presented at IGPP/UCLA on 8 May 2013
Outline
• Introduction
A list of p
published multiple-onset
p
substorm studies enlightened
g
byy
Prof. Chris Russell
• Three phases of multiple-onset substorm studies
“Growth” p
phase: Mapping
pp g consecutive onsets of gground Pi2s to the
incident IMF
“Expansion” phase: Using CANOPUS-MPA, GOES data, Polar UVI
images and LANL energetic electron injections for verification
“Recovery” phase: Using THEMIS data to justify the cause of quiettime Pi2s to be the same as subtorm-time ones
• Summary and conclusion
• Acknowledgments
A k
l d
2
Introduction
Pi2 pulsations,
l ti
in
i a period
i d off 40 tto 150 seconds
d (6-25
(6 25 mHz),
H ) impulsive
i
li
and damped oscillations of geomagnetic fields, associated with
substorm onset [Saito, 1969; Baumjohann and Glassmeier, 1984;
Y
Yumoto,
t 1986;
1986 Olson,
Ol
1999 and
1999,
d references
f
th
therein].
i ]
A group of Pi2s generally occurred successively during substorm onsets
[see review by Saito,
Saito 1969].
1969]
A substorm often has two Pi2s and two individual “bays” in the horizontal
component of the magnetic field denoted as the trigger bay and the
main bay respectively
respectively. [Rostoker,1968]
[Rostoker 1968]
Some evidence of multiple onsets accompanied by Pi2s in a
magnetospheric substorm. [e.g., Kisabeth and Rostoker, 1971;
Clauer and McPherron
McPherron, 1974]
What causes the occurrence of successive Pi2 pulsations during a
magnetospheric substorm is still not well determined
determined.
3
Mishin et al. [2000, 2001] pointed out two distinct onsets in a magnetospheric
substorm of which the first occurs at low latitudes and the second at higher
l tit d
latitudes.
To explain their observations, Russell [2000] extended the near-Earth neutral point
model by Russell and McPherron [1973] with emphasis on the role of the
di t t neutral
distant
t l point.
i t
In the model, the interplay between near-Earth and distant neutral points in the
magnetotail creates two onsets, one when reconnection at the near-Earth neutral
point
i t first
fi t begins
b i on closed
l d field
fi ld lines
li
within
ithi the
th plasma
l
sheet,
h t andd one when
h att
the near-Earth neutral point reaches the open flux of the tail lobes.
The timing of the second substorm onset should be controlled by the distant neutral
point that in turn is controlled by the northward turning of the IMF.
During a magnetospheric substorm, there can be at least two Pi2 bursts in space as
well as on the ground as the incident IMF initially becomes southward for a
period time and later northward.
Thus, it is an important topic to testify the Russell [2000] model with both groundand space – based observations.
Two-neutral-point
T
l i substorm
b
model
d l for
f the
h IMF variation
i i off northh
to-south and then north [Russell, 2000]
Near-Earth
neutral point
Distant-Earth
neutral point
5
A list of published substorm studies enlightened by Prof. Chris Russell
1. Cheng, C.-C., C. T. Russell, Y. F. Gao, and P. J. Chi (2002a), On consecutive bursts of lowlatitude Pi2 pulsations, J. Atoms. Sol. -Terr. Phys., 64, 1809-1821.
2. Cheng, C.-C., C. T. Russell, M. Connors, and P. J. Chi (2002b), Relationship between
multiple substorm onsets and the IMF: A case study, J. Geophys. Res., 107(A10), 1289,
d i 10 1029/2001JA007553
doi:10.1029/2001JA007553.
3. Cheng, C.-C., C. T. Russell, K. Yumoto, Y. F. Gao, and P. J. Chi (2004), Characteristics of
consecutive bursts of Pi2 pulsations observed at the SMALL array: A new implication, Earth
Planet. Space, 56, 531-545.
4 Cheng,
4.
Cheng C.
C -C
C., C
C. T.
T Russell,
Russell G.
G D.
D Reeves,
Reeves M.
M Connors,
Connors and M.
M B.
B Moldwin (2005),
(2005) On the
relationship between double-onset substorm, pseudobreakup, and IMF variation: The 4
September 1999 event, J. Geophys. Res., 110, A07201, doi:10.1029/2004JA010778.
5. Cheng, C.-C., C. T. Russell, and J.-H. Shue (2009a), On the association of quiet-time Pi2
ppulsations with IMF variations, Adv. Space
p
Res., 43, 1118-1129, doi:10.1016/j.asr.2008.12.001.
j
6. Cheng, C.-C., C. T. Russell, V. Angelopoulos, I. Mann, K. H. Glassmeier, U. Auster, and W.
Baumjohann (2009b), THEMIS observations of consecutive bursts of Pi2 pulsations: The 20
April 2007 event, J. Geophys. Res., 114, A00C19, doi:10.1029/2008JA013538.
7. Cheng, C.-C., C. T. Russell, V. Angelopoulos, I. R. Mann, K. H. Glassmeier, and W.
Baumjohann
j h
(2011),
(2011) THEMIS
S observations
b
i
off double-onset
d bl
substorms
b
andd their
h i association
i i
with IMF variations, Ann. Geophys., 29, 591-611, doi:10.5194/angeo-29-591-2011.
“Growth” phase: Mapping Pi2 onsets at SMALL, IGPP/LANL and CPMN to
the IMF sensed by ACE and Wind [Cheng et al., 2002a; 2002b; 2004]
Φ (Mweber)
The southward IMF flux before the
burst #1 onset
Φ =KVXBSΔtDM
Δt: the time interval between
southward IMF turning and the
burst #1 onset.
VX : the average magnitude of the x
component of solar wind velocity.
BS : the average magnitude of the
southward IMF.
K : assumed to be 10%, the percentage
of the southward IMF flux incident
on the magnetosphere.
magnetosphere
DM: assumed to be 30 Re, the nominal
width of the magnetosphere.
t12: the time interval between the burst
#1 onset and the burst #2 onset.
Sketch of substorm current wedge from
McPherron et al. [1973]
Six source mechanisms for nightside
Pi2s [see Yumoto, 2001]
9
Magnetospheric/plasmaspheric
M
h i / l
h i cavity
i resonance modes
d [Cheng
[Ch
et al.,
l EPS,1998,
EPS 1998
2000]
H
comp.
11
“Expansion” phase: Using CANOPUS, GOES, Polar and LANL data
for verification [Cheng et al., 2005]
“Recovery” phase: Using THEMIS data to justify the cause of quiet-time Pi2s to be the
same as substorm-time
bt
ti ones [Cheng
[Ch
ett al.,
l 2009a;
2009 2009b
2009b; 2011]
Fig 1 in Lester et al.
Fig.
al [1984]
Reproduced from Pashin et al.
al [1982]
Current
line
Current
sheet
CCW polarization
A case study of two double-onset substorms [Cheng et al., 2011]
Summary and conclusion
According to Baker et al. [1996], substorm characteristic features in the nearEarth nightside magnetopshere mainly include
bursty bulk flows (BBFs) or fast flows
flows, formation of the current wedge
wedge,
auroral breakups, magnetic bays at high latitudes, Pi2 pulsations.
These features can be found in our multiple-onset
multiple onset substorm events in the
“expansion” and “recovery” phase.
The mapping of ground Pi2 pulsations onset timing to the solar wind
observation just in front of Earth’s magnetopause shows that both bursts
appear under a variation cycle of north to south and then north.
The second Pi2 burst can occurs after a time that is correlated with the
amount of southward IMF convected to the magnetopause.
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The second Pi2 onset can signal that reconnection reaches the tail lobes
after the IMF returns to a northward value.
Wavelet transformations of H and D components at high latitude show
fi t high
first
hi h frequency
f
andd then
th lower
l
one bearing
b i the
th spectral
t l
characteristics of double-onset substorm triggered by northward
turning. But at low latitudes, their dominant frequency seems to close
to each other.
Waveform comparisons show that Pi2 can result from a combination of
fast magnetospheric and plasmaspheric cavity resonances due to
braking
g earthward fast flows. In addition, theyy can result from
coupling to field line resonances.
The source mechanism of Pi2s at times of weak geomagnetic activity can
be the same as during substorms.
Hence, the two-neutral-point model by Russell [2000] can explain the
occurrence of multiple-onset substorms due to magnetic reconnection
in the near
near-Earth
Earth region and the distant
distant-Earth
Earth one respectively under
IMF variations.
20
A k
Acknowledgments
l d
t
We would like to thank all the data pprovider for
use in multiple-onset substorm studies. This work
was supported under the grant by National
Science Council of R. O. C. on Taiwan.
Thank you for your attention.
Happy 70th birthday to Chris !
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