CME Propagation

CSI 769 / ASTR 769 Lect. 11, April 10 Spring 2008

CME Flux Rope Model

Lepping, R.P., Jones, J.A., Burlaga.“Magnetic Field Structure of Interplanetary Magnetic Clouds at 1 AU”JGR, Vol. 95, No. A8, 11957-11965, 1990

CME MSOE Model

Siscoe, 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

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

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

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SH (Shock Sheath)

Solar Sources

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)

Corotating Interaction Region (CIR)•When a low latitude coronal hole appears (across the heliographic equator), fast wind exists in the ecliptic plane.

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

CIRCorotating Interaction Region: Caused by the interaction of fast SW originated from

coronal hole with preceding slow SW CIR/SI

IMF

The End