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

Presentations PresenterTopic/QuestionFuture Plans J.-L. BougeretGlobal SunHomolog. CMEs R. Canfield Separatrix surfaces,  sCDAW 1999 data for CME-  connection S. Antiochos Bipole  shear   Seehafer  -effect builds up helicity; released in CMEs Use SOHO/MDI data D. MaiaNonthermal brightening & Filament eruption Do statistics N. GopalswamyMicrowave filament &X-ray brightening Chen/ShibataFilament Eruption & Emerging Flux Simulation K. DereAR evolution & CMEsUse Lara et al. (2000) method N. GopalswamyPhotospheric B flux changeDo Statistics S.AntiochosInputs to CME models N. GopalswamyNonradial 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

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-Dimming G- 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 B z reversal line -- B-supports prominences/filaments

Summary of Numerical Models of CMEs Model Forbes et al., 1994 Linker, et al 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 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 (

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