CME Propagation

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CME Propagation
CSI 769 / ASTR 769 Lect. 11,
April 10 Spring 2008
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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
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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
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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 Tp Texp ß Sun
2004/07/27 storm (-182 nT)
Shock Front discontinuity

• ICME (ejecta)
• B enhance
• Bz rotation
• Low Plasma ß
• Low Tp
• High QFe
• -----

SH (Shock Sheath)
Solar Sources
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Fast and Slow Wind
Solar Wind Bimodal
Fast wind originates from coronal hole, Slow
wind originates from regions close to streamer
belts or heliospheric current sheet
SW heliographic latitudinal Distribution (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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CIR
Corotating 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