Formation of hot channels in pre-CME coronal flux ropes and their role in the onset of eruptions
Coronal Mass Ejection (CME)
description
Transcript of Coronal Mass Ejection (CME)
The Structure of Magnetic Clouds in the Inner Heliosphere: An Approach
Through Grad-Shafranov Reconstruction
Qiang Hu, Charlie J. Farrugia, V. Osherovich, Christian Möstl,
Jiong Qiu and Bengt U. Ö. Sonnerup
ILWS Workshop 2011
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Coronal Mass Ejection (CME)
(Moore et al. 2007)
Simultaneous multi-point in-situ measurements of an Interplanetary CME
(ICME) structure(Adapted from STEREO/IMPACT website, http://sprg.ssl.berkeley.edu/impact/instruments_boom.html)
3in-situ spacecraft data
Cylindrical flux-rope model fit (Burlaga, 1995; Lepping et al., 1990, etc.)
Modeling of Interplanetary CME
4x: projected s/c pathx: projected s/c path
-VHT
Grad-Shafranov Reconstruction method: derive the axis orientation (z) and the cross section of locally 2 ½ D structure from in-situ single spacecraft measurements (e.g., Hu and Sonnerup 2002).
•Main features:
- 2 ½ D
- self-consistent
- non-force free
- flux rope boundary definition
- multispacecraft
actual result:actual result:
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• Output:1. Field configuration2. Spatial config.3. Electric Current.4. Plasma pressure p(A).5. Magnetic Flux :
- axial (toroidal) flux t= Bzxy- poloidal flux p=|Ab - Am|*L
• Relative Helicity:Krel=2L A’· Bt dxdy
A’=Bzz^
GS Reconstruction of ICME Flux Ropes (1D2D)
• Ab
Am
ACE Halloween event (Hu et al. 2005)
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• Relative magnetic helicity (Webb et al. 2010):
Bz(x,y)
rKr/AU: 3.5x1023 Wb2
Kr/AU (Hu and Dasgupta, 2005):
3.4x1023 Wb2
ˆ2 ' , ' ', 'r t zVK dV B A B A B B z
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poloidal or azimuthal magnetic flux P:
the amount of twist along the field lines
The helical structure, in-situ formed flux rope, results from magnetic reconnection.
toroidal or axial magnetic flux t
Longcope et al (2007)
ribbons
poloidal flux P
reconnection flux r
reconnection
3D view: one scenario of flux rope formation3D view: one scenario of flux rope formation3D view: one scenario of flux rope formation3D view: one scenario of flux rope formation
(Gosling et al. 1995)
(Moore et al. 2007)
Credit: ESA
reconnection
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• Comparison of CME and ICME fluxes (independently measured for 9 events; Qiu et al., 2007):
- flare-associated CMEs and flux-rope ICMEs with one-to-one correspondence; - reasonable flux-rope solutions satisfying diagnostic measures; - an effective length L=1 AU (uncertainty range 0.5-2 AU) .
GS method
Leamon et al. 04
Lynch et al. 05
P ~ r
• Recent modeling and comparison of flux-rope flux and helicity contents (Kazachenko et al. 2011)
• GS Reconstruction of Locally Toroidal Structure
(Freidberg 1987)
Z
R
O
A torus of arbitrary cross section
s/c
Sun
O’
O
Z’R
r
t
(r, t) plane projection
r’
R s/c path
O (O’)Z’.
(R, ) plane projection
(R, , Z) axes (Z: rotation axis; : torus axis):
Search grid on (r,t) plane
Boundary of the torus
(Farrugia et al. 2011)
Sun
Wind ST-AST-B
Acknowledgement: Dr. J. Luhmann of UCB/SSL, and Dr. Antoinette Galvin of the University of New Hampshire, and NASA CDAWeb.
•Effect of Te (2007/01/13 00:00:00 - 2007/01/17 00:00:00 DOY 013-017)
<Te/Tp>~12<>~0.24
• The GS reconstruction map for the case w/o (left window) and w/ (right) Te contribution, respectively
• The corresponding Pt(A)=p+Bz/20 fitting2
Event 2005/10/30 00:00:00 - 2005/11/02 00:00:00 DOY 303-306
<Te/Tp>~4<>~1
• The GS reconstruction map for the case w/o (left window) and w/ (right) Te contribution, respectively
• The corresponding Pt(A) fitting
Concluding Remarks
• Quantitative CME-ICME comparison provides essential insight into the underlying mechanism(s)
• Also provides validation of data analysis methods/results
• Torus-shaped geometry provides an alternative view of MC flux rope; will complement the existing analysis
• The effect of Te is limited to contribution to the plasma and pressure; it is the gradient of pressure that matters
… Fully 3D?
z r
RSun
])2[(]/)/1[(
02
02
2
d
dGG
d
dpr
zr
rrr
GS equation:(R. H. Weening, 2000)
A torus of arbitrary cross section?