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CME Propagation
CSI 769 / ASTR 769 Lect. 11, April 10 Spring 2008
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CME Flux Rope ModelLepping, R.P., Jones, J.A., Burlaga.“Magnetic Field Structure of Interplanetary Magnetic Clouds at 1 AU”JGR, Vol. 95, No. A8, 11957-11965, 1990
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CME MSOE ModelSiscoe, G.L., Crooker, N.U., Elliott, H.A., “Initial-Condition Influences on CME Expansion and Propagation”Solar Physics, Vol. 239, 293-316, DOI: 10.1007/s11207-006-0302-3, 2006
MSOE: Melon-Seed-Overpressure-Expansion Model
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Interplanetary CME (ICME)•CME propagates into the interplanetary space, plowing through the ambient solar wind•The magnetic structure of ICME at 1 AU is similar to that in its solar origin, which is highly helical (called flux rope)•At 1 AU, it is called magnetic cloud
•highly organized magnetic field is observed, e.g., smooth rotation•Large scale, crossing the Earth for ~ 24 hours
Magnetic Cloud
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ICME Identification Dst
B/Bz
Vel
Np
TpTexp
β
Sun
2004/07/27 storm (-182 nT)
Shock Front: discontinuity
ICME (ejecta): • B enhance• Bz rotation• Low Plasma β• Low Tp• High QFe
• -----
SH (Shock Sheath)
Solar Sources
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Solar Wind: BimodalFast wind originates from coronal hole,
Slow wind originates from regions close to streamer belts or heliospheric current sheet
SW heliographic latitudinalDistribution (Ulysses observation)
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Corotating Interaction Region (CIR)•When a low latitude coronal hole appears (across the heliographic equator), fast wind exists in the ecliptic plane.
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Corotating Interaction Region (CIR)•The jetline of fast wind is less curved than that of slow wind•Fast streams “catching up” with slow streams, compressing the preceding stream and produce a high pressure region.•The interaction region is at the leading edge of the fast stream•Since low-latitude coronal holes can live over several solar rotations, this structure can recur several times•This is commonly called “corotating interaction region” or CIR•A pair of forward and reverse shocks forms
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CIRCorotating Interaction Region: Caused by the interaction of fast SW originated from
coronal hole with preceding slow SW CIR/SI
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IMF
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The End