Working Group E: The Pre-CME Sun

- Pre-eruption structure, evolution & energy release

- Global issues: helicity, homologous CMEs

- Inputs to CME initiation models

N. Gopalswamy

From First Elmau CME workshop

PresentationsPresenter Topic/Question Future Plans

J.-L. Bougeret Global Sun Homolog. CMEs

R. Canfield Separatrix surfaces, s CDAW 1999 data for CME- connection

S. Antiochos Bipoleshear

Seehafer -effect builds up helicity; released in CMEs

Use SOHO/MDI data

D. Maia Nonthermal brightening & Filament eruption

Do statistics

N. Gopalswamy Microwave filament &X-ray brightening

Chen/Shibata Filament Eruption & Emerging Flux

Simulation

K. Dere AR evolution & CMEs Use Lara et al. (2000) method

N. Gopalswamy Photospheric B flux change Do Statistics

S.Antiochos Inputs to CME models

N. Gopalswamy Nonradial Motion of filaments

Structure of CMEs

• Frontal structure

• Cavity

• Prominence Core

• Post-eruption Arcade (Two-ribbon in H-alpha, arcades in X-ray, EUV)

• Note: Not all structures are present in all CMEs!

‘Cavity’ in Eclipse Pictures

Where do CMEs originate?

• CMEs originate from closed field regions

- Active Regions

- Filament regions

- Combination of AR and Filament regions

- Transequatorial interconnecting regions

Closed Field Regions: Where one should look for pre-CME signatures

TIL

Filament

Active region

SOHO/EIT image 195 A H-alpha picture

• Structure (Sigmoids, Flux Ropes)

• Evolution (Flux Emergence, Flux cancellation, Shear, Twist)

• Energy Release (Small-scale Heating & Particle Acceleration)

Aspects of Pre-eruption Phase

Three-part structure before eruption (Yohkoh/SXT)

• Frontal (but sheared)

• Cavity hidden?

• Filament core

Pre-Eruption Structure:Sigmoids

• 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)

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 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)

Pre-eruption Structure:Guiding Streamers

• Non-radial motion of filaments

• Obvious during Solar Minimum

• Latitudinal distribution of CMEs peaks near the equator; associated solar sources peak near the active region belt

The solar dipole field has strong influence on CME propagation

CME CPAs equatorward of

Prominence CPA during min

• Compared 186 microwave prominences with LASCO CMEs during 1996-2001

Pre-eruption Evolution• Substantial Flux emergence near filament before

eruption; polarity of new flux favorable for reconnection (Feynman & Martin, 1995)

- Confirmed by 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

Simulation supports preeruption Reconnection (Chen & Shibata 2000)

• Flux emergence under the filament

• Flux emergence from the side

A transequatorial Eruption

• EIT 195 A difference image showing dimming at 08:36 UT

• LASCO image at 08:56 UT

Weak Dimming Before Eruption

AR-Active Region D-DimmingG- GOES X-ray Flux

Pre-eruption Evolution: Prolonged Dimming

• Weak, prolonged dimming for ~ 1 hr (Gopalswamy et al., 2001)

• Small-scale opening of field lines resulting in the eruption of underlying structure? (Antiochos et al., 1994)

Pre-eruption Energy Release

• Small-scale heating near filaments - consistent with reconnection scenario• Particle Acceleration- Radio bursts (400 MHz) near filaments

(Maia et al.)- Minutes before filament eruption- nonthermal energy release due to

reconnection

Filament Eruption Onset

Models: Goal & Observational Inputs

• Goal of Models:- High velocity (> 1000 km/s) opening of field

• Inputs:- Slow photospheric driving:-- emergence/submergence of flux-- shear/twist- B-stressing concentrated near Bz reversal line-- B-supports prominences/filaments

Summary of Numerical Models of CMEs

Model

Forbes et al., 1994 Linker, et al. 2001

Chen and Shibata, 2000

Antiochos et al., 1994

Wu et al., 2000

Chen et al., 1997

Pre-Eruption Structure

Flux rope in bipolar field: either emerges or forms in the corona

Flux rope in multipolar field

Sheared arcade in multipolar field

Flux rope with overlying streamer in the solar wind

Flux rope in equilibrium

Pre-eruption Evolution

Flux decrease/changes leading to loss of equilibrium

Flux emerges consistent with reconnection

Continued shearing

Increase in the azimuthal flux or shear of the streamer field

Increase in the azimuthal flux

Pre-eruption Energy Release

None

Reconnection energization at the site of emergence

Reconnection energization at coronal null/separator  

None

None

Caution: This table is incomplete, mainly initiation

Homologous CMEs?

• Homologous flares are known: flares from the same region with same morphology and similar light curves.

• Are there homologous CMEs?- multiple CMEs from the same region• Candidate events: transequatorial CMEs

during April 27-May 8, 1998 (http://cdaw.gsfc.nasa.gov)

CMEs and Helicity - Solar Dynamo builds up helicity- Released by CMEs

• Use full-disk MDI magnetograms to calculate global distribution of H (assuming B to be constant over certain time intervals & exploiting the fact that B is seen different directions).

• Compare global helicity distribution and evolution with appearance of CMEs.

• Use vector magnetograms to study helicity and CMEs in active regions in comparison with the helicity of the global B.

“Reconnection-favoring” Flux Emergence

2000/09/12 SXR & H-alpha

Pre-eruption

Post-eruption

Energy Release Near Filament

Filament Eruption in EUV

• SOHO/EIT (195 A) images presented as a movie.

• The NW-SE filament in the southern hemisphere erupts and becomes the core of the white light CME

• Arcade formation follows the eruption

H-alpha:Before and After Eruption

2000/09/12 CME on the Disk

• SOHO/LASCO C3 movie

• Partial halo event consistent with the southern location on the disk

• The bright core is the filament

2000/09/12 CME in LASCO/C2

CMEs and ICMEs:A tentative correspondence

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

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