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Coronal current sheet signatures during the 17 May 2002 CME-flare  

Henry Aurass   Submitted: 2009-08-20 04:50

The relation between current sheets (CSs) associated with flares, revealed by characteristic radio signatures, and current sheets associated with Coronal Mass Ejections (CMEs), detected in coronal ultra-violet (UV) and white light data, has not been analyzed, yet. We aim at establishing the relationship between CSs associated with a limb flare and CSs associated with the CME which apparently develops after the flare, on the basis of a unique data set, acquired on May 17, 2002, which includes radio and extreme ultra-violet (XUV) observations. Spectral radio diagnostics as well as UV spectroscopic techniques together with white light coronograph imaging and (partly) radio imaging are used to illustrate the relation between the CSs and to infer the physical parameters of the radially aligned features that develop in the aftermath of the CME. During the flare, drifting pulsating structures in dynamic radio spectra, an erupting filament, expanding coronal loops morphologically reminding to the later white light CME and associated with earlier reported hard X-ray source sites, are interpreted in accordance with earlier work and with reference to the common eruptive flare scenario as evidence of flare CSs in the low corona. In the aftermath of the CME, UV spectra allowed us to give an estimate of the CS temperature and density, over the 1.5 - 2.1 Rs interval of heliocentric altitudes. The UV detected CS, however, appears to be only one of many current sheets that exist underneath the erupting flux rope. A type II burst following in time at lower frequencies the CME radio continuum is considered as radio signature of a coronal shock excited at the flank of the CME. The results show that we can build an overall scenario where the CME is interpreted in terms of an erupting arcade crossing the limb of the Sun and connected to underlying structures via multiple CSs. Eventually, the observed limb flare seems to be a consequence of the ongoing CME.

Authors: H. Aurass, F. Landini, G. Poletto
Projects: None

Publication Status: A & A accepted
Last Modified: 2009-08-20 07:55
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The GLE on Oct. 28, 2003 - radio diagnostics of relativistic electron and proton injection  

Henry Aurass   Submitted: 2006-08-31 03:00

Timing discrepancies between signatures of accelerated particles at the sun and the arrival times of the particles at near-earth detectors are a matter of fundamental interest for space-weather applications. The solar injection times of various components of energetic particles were derived by Klassen et al. (2005) for the October 28, 2003, X-class / gamma-ray flare in NOAA AR10486. This flare occured in connection with a fast halo coronal mass ejection and a neutron monitor-observed ground level event (GLE). We used radio (Astrophysikalisches Institut Potsdam, WIND, Nancay Multifrequency Radio Heliograph), Halpha (Observatorium Kanzelhoehe), RHESSI, SOHO (EIT, LASCO, MDI), and TRACE data to study the associated chromospheric and low coronal phenomena. We identify three source sites of accelerated particles in this event. Firstly, there is a source in projection 0.3Rs away from AR10486, which is the site of the reconnection outflow termination, as revealed by a termination shock signature in the dynamic radio spectrum. Secondly, there is the extended current sheet above a giant coronal postflare loop system in the main flare phase. Thirdly, there is a source situated on a magnetic separatrix surface between several magnetic arcades and neighbouring active regions. This source is 0.2Rs away from AR10486 and acts during onset and growth of high energy proton injection in space. It is not clear if this source is related to the acceleration of protons, or if it only confirms that energetic particles penetrate a multistructure magnetic loop system after being previously accelerated near the main HXR- and gamma-ray sources. The result is in favour of energetic particle acceleration in the low corona (<0.5Rs above the photosphere) and in contrast to acceleration of the relativistic particles at remotely propagating shock waves.

Authors: H. Aurass, G. Mann, G. Rausche, and A. Warmuth
Projects: RHESSI,SoHO-EIT,SoHO-MDI,TRACE

Publication Status: A&A 2006 in press
Last Modified: 2006-08-31 10:17
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Coronal current sheet signatures during the 17 May 2002 CME-flare
The GLE on Oct. 28, 2003 - radio diagnostics of relativistic electron and proton injection

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