It s Magnetic Cloud Illusions, I Recall:
It’s
Magnetic Cloud Illusions I Recall:
Shifting Paradigms with Chris Russell
Tamitha Mulligan and Chris T. Russell
A Celebration of a Life in Science
May 8 2013
May 8, 2013
Recipe for Paradigm Shift
p
g
P di
Paradigm Shift
Shift
ICME Paradigm circa 1996
•
HCS
•
•
•
Piddington [1958] and Gold
[1962] first recognized that the
Sun’s dipolar magnetic field
should be pulled out into
space.
Current paradigm implies
global dipole field of Sun
threads the axis of
interplanetary coronal mass
ejections (ICMEs)
Magnetic ropes are formed
when the dipole field gets
twisted
Approximately one-third of all
ICMEs have a topology
similar to the magnetic cloud
flux rope
In Vogue Flux Rope Model of ICMEs
•
Cylindrical force-free flux rope
based on Lundquist [1950]
B
Bessel
l ffunction
ti solutions
l ti
•
Returns axial orientation,
diameter, field strength, and
impact parameter of magnetic
clouds Burlaga [1981]
•
Force balance achieved without
consideration of plasma regime
•
limited to straight-cylindrical
symmetry, static force-free
geometry with no consideration
for expansion
Non‐Force Free Flux Rope Model
[M lli
[Mulligan
and
dR
Russell,
ll 2001]
Motivation Behind Multi‐Spacecraft Model Development Development
•
The PVO and ISEE 3
spacecraft observe same MC
on 27 August
g
1978 while
separated by 12° in azimuth
•
Single spacecraft FR model fits
to PVO and ISEE-3 data results
i ttwo adjacent
in
dj
t cylindricallyli d i ll
symmetric ropes having similar
orientations and driving the
same shock
•
Fitting the PVO and ISEE 3
simultaneously results in a noncylindrically-symmetric FR with
an azimuthal
i th l di
dimension
i 4
4x it
its
radial thickness and 5x flux
content of ISEE-3 rope
Non‐Force Free, Non‐Cylindrically Symmetric, Non Single Spacecraft Flux Rope Model
Non‐Single Spacecraft Flux Rope Model
•
Modeling multispacecraft
observations
b
ti
means
modeling larger-scale
features of flux ropes:
– Azimuthal stretching
g
– (ie non-cylindrical
cross-sections)
– Axial curvature
– Better constraints on
expansion
Complex Flux Rope Geometries
•
Multispacecraft
observations of ICMEs
also raised new
questions about largescale ICME structure at
larger spacecraft
separation distances
•
Not all flux rope
observations were easy
to interpret
p ((or to model!))
•
We really needed a
plasma instrument on
NEAR
•
Apparently, there is a
limit to the magic of
Goldfish
Solar Cycle Variation Studies: Classification Scheme
N
W
S
E
W
S
Flux Rope Orientation V i O
Varies Over Solar Cycle
S l C l
•
Statistical study of Pioneer Venus Orbiter
(PVO) dataset 1979-1988
•
Orientation of MC axes has a 22-year
p
periodicity
y
•
High inclination MCs maximize at the
declining phase of the solar cycle during
the maximum dipolar inclination of the
streamer
t
belt
b lt neutral
t l line
li [Zhao
[Zh and
d
Hoeksema 1981]
•
Leading polarity of low inclination MCs
reverses with the global polar field of the
Sun
New Observational CME Model
•
•
Hoeksema and Schrerrer
[1986] synoptic maps of
the streamer belt
orientation correlate with
ICME FR model
orientations at 0.7 AU
For flux ropes originating in
the streamer belt:
– Leading FR field
orientation corresponds
to overlying arcades at
2.5 Rs
– Axial field correlates
with the magnetic
ne tral line direction
neutral
(with a 180° ambiguity)
– Handedness is not
predictable with this
method
th d
Revised Paradigm of ICMEs
•
Over 80% of all predictions of
MC orientation are within 45º
of actual (only handedness of
MCs remaining ambiguous)
•
Confirmed the dipole field of
the Sun controls the leading
g
polarity of the azimuthal field in
magnetic ropes
•
Coronal streamer belt
orientation controls axial field
f
orientation in ICMEs fromthis
region
•
CMEs form in the plane of the
HCS not perpendicular to it
Mulligan et al. [1998]
HCS plane
Beyond UCLA Chris Inspired Advancements
Lindsay, 1996
Kilpua et al., 2010
•
Gretchen Lindsay velocity flow
deflections for non-flux rope
signatures
•
Spatial mapping of ICMEs
[[Mulligan
g et al.,, 2013]]
Parting Thoughts
•
It’s cloud illusions I recall, I really don’t know
clouds at all
all.
– Elusive CME-ICME connection has yet to
be made
– Topological connections to source region
still a mystery
•
Chris continues to inspire