Coronal Mass Ejections 4: Modeling CMEs

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Coronal Mass Ejections 4Modeling CMEs

• Pre-eruption state
• (Structure, Evolution, Energy Release)
• Summary of Models
• Dynamical Types of CMEs
• (based in inverse and normal polarity
  configurations)

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Flare-based CME models

• Flare represents a pressure pulse.
• The pulse duration is the duration of the flare
• Flare has to precede the CMEs
• Flare energy and the CME kinetic energy must be
  tightly correlated

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CME Models Prominence Eruption

• Filament activity precedes eruption (Martin and
  Ramsey, 1972) Recall Sept 11, 2000 event
• Formation and Eruption of Prominences is central
  to CME models
• As CME drivers (Filippov, 1996)
• Reduction of Prominence mass for the onset of
  CMEs (Low and Zhang, 2002)
• However, Hundhausen (1999) thinks that
  prominences eruptions are not energetically
  favorable to drive CMEs.

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Aspects of Pre-eruption Phase

• Structure (Helmet Streamers, Sigmoids, Flux
  Ropes)
• Evolution (Flux Emergence, Flux cancellation,
  Shear, Twist)
• Energy Release (Small-scale Heating
  Acceleration Thermal and nonthermal signatures)

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Three-part structure before eruption (Yohkoh/SXT)

• Frontal (but sheared)
• Cavity hidden?
• Filament core

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Pre-Eruption StructureSigmoids

• S- and reverse S-shaped structures in X-ray
  images of Active Regions (Rust Kumar 1996).
• Erupt more often than non-sigmoidal regions
  (Canfield et al. 1999) Beware of apparent
  sigmoids (Glover et al., 2000)
• Relation to white light CMEs being studied
• Coronal counterpart of photospheric shear
  (Ambastha et al., 1993)

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Sigmoid

• Yohkoh SXT images of an active region before and
  after CME eruption

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Pre-eruption Structure Flux ropes

• Naturally support prominences (Linker et al.,
  2001)
• Often observed as dark cavity in eclipse pictures
• Formed before (Low, 2001) or during (Gosling et
  al., 1990) eruption?
• Interplanetary Magnetic Clouds (MC) are flux
  ropes (Burlaga et al.,1981)
• MC formed out of filament or cavity of the white
  light CME? (Bothmer Schwenn, 1994 Gopalswamy
  et al., 1998)

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Cavity in Eclipse Pictures
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A Cartoon Model of an MC

• Width, curvature found from multi-spacecraft
  (Helios 1, Voyager 2 Helios 2) Observations
• Flux Rope Structure from Force Free equilibrium
  calculations
• (Based on Burlaga,
• et al 1981)

Ecliptic plane
IMP8, He 2
AXIS
.3 AU
He 1
Mag. Pressure gt Ambient Pressure
Vo2
Width 0.25 AU
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CMEs and ICMEsA tentative correspondence

• CMEs Near Sun
• Shock ?
• Frontal ?
• Cavity ?
• Prominence Core ?
• Arcade Formation

• ICMEs near Earth
• Shock
• Sheath
• Ejecta/MC
• Pressure Plug
• --------------

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Pre-eruption Evolution

• Flux emergence, submergence/cancellation
• Shear
• Mass loading (Wolfson, 1989)
• High coronal reconnection (Antiochos et al.,
  1994 Low and Zhang, 2002)
• Poloidal flux injection (Chen, 1997 Wu et al.,
  1999)

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Pre-eruption EvolutionFlux Emergence

• Substantial Flux emergence near filament before
  eruption polarity of new flux favorable for
  reconnection (Feynman Martin, 1995)
• - Consistent with numerical simulation studies
  (Chen Shibata, 2000)
• Significant changes in photospheric flux in
  small areas in the eruption region (Lara et al.,
  2000)
• CMEs without flux emergence also observed
  (Subramanian Dere, 2001 Wang Sheeley, 1999)
• Reconnection-favoring flux emergence

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Weak Dimming Before Eruption
AR-Active Region D-Dimming G- GOES X-ray Flux
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A transequatorial Eruption

• EIT 195 A difference image showing dimming at
  0836 UT
• LASCO image at 0856 UT

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Pre-eruption Evolution Prolonged Dimming

• Weak, prolonged dimming for 1 hr (Gopalswamy et
  al., 1999)
• Small-scale opening of field lines resulting in
  the eruption of underlying structure? (Antiochos
  et al., 1994 Low and Zhang, 2002)

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Streamer Distension Eruption
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Pre-eruption Energy Release
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Pre-eruption Energy Release

• Signatures of pre-eruption energy release
• Small-scale heating near filaments, consistent
  with reconnection scenario (Feynman and Martin,
  1995)
• - Radio bursts near filaments nonthermal energy
  release due to reconnection (Jackson et al.,
  1978 Marque, 2001- Nancay Observations)

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Energy Release Near Filament
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Filament Eruption Onset
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Reconnection-favoring Flux Emergence
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Simulation supports preeruption Reconnection
(Chen Shibata 2000)

• Top Flux emergence under the filament
• Bottom flux emergence from the side

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Summary of Numerical Models of CMEs
Caution This table is incomplete, mainly
initiation
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Flux-rope expulsion Inverse Configuration
Flux-rope field Surface field in the opposite
direction
Low and Zhang, 2002
Jf ltgtJcs RC not needed
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Example from SXR H-alpha
Pre-eruption
Post-eruption
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Flux-rope expulsion Normal Configuration
Flux-rope field Surface field in the Same
direction
Low and Zhang, 2002
Jf gtltJcs RC needed
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CMEs from Normal Inv Ropes

• Normal Polarity
• CS above flux rope
• Rapid acceleration
• No arcade?
• Deceleration possible from eruptive config
• FR-ambient reconnection

• Inverse Polarity
• CS below flux rope
• Gradual acceleration
• Post-ruption arcades
• No deceleration expected
• No FR-ambient field reconnection

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Summary of Forces

• Propelling Forces Hoop force, hydromagnetic
  buoyancy force. Problem How these are
  distributed in the pre-eruption stage and how the
  balance is lost.
• Retarding forces Gravity (M), Coronal Drag (V)

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Fe Ratio Can Identify CME

• Fe Ratio - the fraction of high-charge state (
  16) Fe ion density relative to the total Fe
  density in all charge states (plotted ratio X
  200) (Lepri et al., 2001)
• Short-lived intense geomagnetic storm follows
  immediately after the shock ? sheath

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Prominences

• Type A,B,C filament
• A bipolar, B-between bipolar, C-between polar
  crown and active belt B most common (2/3 F.
  Tang)
• Polarity Normal (KS), Inverse (KR)
• Chirality (Foukal, Marin)
• Sinister/southern dextral/northern does not
  tell you about helicity
• Sinistral normal ? RH
• F Channel Chae et al. (2001)

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Prom B

• Zirin Severny (1961) first meas
• On disk Harvey (2001)
• Hanle depolarization by local B Leroy et al.
  (1977) On disk Lin (1998)

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Eruption

• Flux Cancellation bifurcation of F
• What causes formation? Are they flux rope?
  Tightly bound flux
• What activates filament?
• Can the statistics of Leroy taken for granted
• Is the global pattern fundamental for Phys?

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Flares

• Posflare loops
• Bastille day event two eruptions?
• Standard flare model Sturrock (1968) single
  bipolar region
• Cusp in Yohkoh RC?
• Yokoyamas reconnection example
• Loop intercation model different from standard
  flare model?

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Negative Associations

• Continuous vs explosive
• Two step RC 1. Cancellation 2. Explosive flare
  is second, Mathew Ambastha (2000), Ji et al
  (2001a,b,c), Livinenko (1999) H.Wang et al.
  (2002)
• Q What is the preflare config?
• Irreversible Impulsive changes?
• Primary release site?
• Zhou et al., 2002 92 PE ass. With CMEs
• 990205 flux rope

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Flux Rope

• Curren carrying emerging flux (Chen, 2001)
• Filament (Rsut Kumar, 1994) continuos dist. Of
  dip
• Cavity (Low, 1996) van Ball Martens (1989)
• Plasmoid (Shibata, 2001)
• Yan et al. (2001)
• Nature of dimming
• Large-scale field structure hosting CMEs TIL,
  Long channel, Sigmoid
• Cancellation only detectable magnetic change
• Forbes et al.
• 10filament eruption