Non-thermal processes associated with rising structures and waves during a “halo” type CME

Free access article

Issue		A&A Volume 442, Number 3, November II 2005


Page(s)		1049 - 1058
Section		The Sun
DOI		http://dx.doi.org/10.1051/0004-6361:20041376

A&A 442, 1049-1058 (2005)
DOI: 10.1051/0004-6361:20041376

Non-thermal processes associated with rising structures and waves during a "halo" type CME

N. J. Lehtinen¹, S. Pohjolainen¹, M. Karlický², H. Aurass³ and W. Otruba⁴

¹ Tuorla Observatory/VISPA, University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
e-mail: nijole@utu.fi
² Astronomical Institute of the Academy Sciences of the Czech Republic, 25165 Ondrejov, Czech Republic
³ Astrophysical Institute Potsdam, 14482 Potsdam, Germany
⁴ Sonnenobservatorium Kanzelhöhe, 9521 Treffen, Austria

(Received 31 May 2004 / Accepted 21 March 2005 )

Abstract
We analyse structures and events connected with a flare-associated "halo" type coronal mass ejection (CME) observed on December 18, 2000. A GOES C7.0 class X-ray flare started at 11:02 UT in NOAA Active Region 9269, located at N14 E03. Yohkoh SXT observed slowly rising soft X-ray loops already some 5 min before flare start. H ${\alpha}$ images show a two-ribbon flare, remote brightenings, and a partly disappearing filament near the active region. A metric radio precursor was observed to start at 11:06:30 UT, simultaneously with impulsive emission in hard X-rays and microwaves. The frequency-drifting precursor envelope was superposed with J- and reverse drift bursts. The radio bursts traced large-scale soft X-ray loop structures about 160 000 km away from the flare core, and hard X-ray emission was observed at the ends of some of these loops. The precursor emission points to a rising structure where electron acceleration takes place. Later on, a radio type II burst (signature of a propagating shock, driven either by an ejecta or a blast wave) and an EIT wave were observed. We conclude that possible sources for the rising structure and accelerator of electron beams are (1) large-scale loops that connect the flare core region and the precursor site in the close vicinity of two separate rising filaments, and (2) a growing shock that accelerates electrons along closed field lines until the multipolar field is opened and the CME is lifted off. As neither X-ray nor EUV ejecta could be observed whether in the direction of the type II burst or near the radio precursor, we find some support for the shock wave scenario.

Key words: Sun: corona -- Sun: coronal mass ejections (CMEs) -- Sun: filaments -- Sun: flares -- Sun: radio radiation -- Sun: X-rays, gamma rays

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