Responsibility of a Filament Eruption for the Initiation of a Flare, CME, and Blast Wave, and its Possible Transformation into a Bow Shock
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Multi-instrument observations of two filament eruptions on 24 February and 11 May 2011 suggest the following updated scenario for eruptive flare, coronal mass ejection (CME), and shock wave evolution. An initial destabilization of a filament results in stretching out of the magnetic threads belonging to its body that are rooted in the photosphere along the inversion line. Their reconnection leads to i) heating of parts of the filament or its environment, ii) an initial development of the flare cusp, arcade, and ribbons, iii) an increasing similarity of the filament to a curved flux rope, and iv) to its acceleration. Then the pre-eruption arcade enveloping the filament becomes involved in reconnection according to the standard model and continues to form the flare arcade and ribbons. The poloidal magnetic flux in the curved rope developing from the filament progressively increases and forces its toroidal expansion. This flux rope impulsively expands and produces a magnetohydrodynamical disturbance, which rapidly steepens into a shock. The shock passes through the arcade that expands above the filament and then freely propagates for some time ahead of the CME like a decelerating blast wave. If the CME is slow, then the shock eventually decays. Otherwise, the frontal part of the shock changes into the bow-shock regime. This was observed for the first time in the 24 February 2011 event. When reconnection ceases, the flux rope relaxes and constitutes the CME core–cavity system. The expanding arcade develops into the CME frontal structure. We also found that reconnection in the current sheet of a remote streamer forced by the shock passage results in a running flare-like process within the streamer responsible for a type II burst. The development of dimming and various associated phenomena are discussed.
KeywordsFilament eruptions Flares Coronal mass ejections Shock waves Type II bursts
We appreciate the efforts of the colleagues operating SSRT and NoRH. We thank G. Rudenko, S. Anfinogentov, K.-L. Klein, K. Shibasaki, L. Kashapova, N. Meshalkina, and Y. Kubo for their assistance and discussions and the anonymous referees for useful remarks. Our special thanks go to the second referee for the valuable recommendations that significantly helped us to bring this article to its final form. We are grateful to the instrumental teams operating SDO/AIA, STEREO/SECCHI, Wind/WAVES and S/WAVES, RHESSI, SOHO/LASCO (ESA & NASA), NICT, Culgoora Radio Spectrograph, USAF RSTN network, and GOES satellites for the data used here. We thank the team maintaining the CME Catalog at the CDAW Data Center by NASA and the Catholic University of America in cooperation with the Naval Research Laboratory. This study was supported by the Russian Foundation of Basic Research under grants 11-02-00757, 12-02-00037, 12-02-33110-mol-a-ved, 12-02-31746-mol-a, and 14-02-00367; the Integration Project of RAS SD No. 4; the Program of basic research of the RAS Presidium No. 22, and the Russian Ministry of Education and Science under projects 8407 and 14.518.11.7047.
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