The GLE on Oct. 28, 2003 – radio diagnostics of relativistic electron and proton injection

Abstract

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, JGR, 110, A09S04) for the October 28, 2003, X-class/ γ -ray flare in NOAA AR 10486. 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, $\emph{WIND}$, Nancay Multifrequency Radio Heliograph), H α (Observatorium Kanzelhohe), $\emph{RHESSI}$, $\emph{SOHO}$ (EIT, LASCO, MDI), and $\emph{TRACE}$ 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 0.3 $R_\odot$ away from AR 10486, 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 0.2 $R_\odot$ away from AR 10486 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 γ -ray sources. The result is in favour of energetic particle acceleration in the low corona (<0.5 $R_\odot$ above the photosphere) and in contrast to acceleration of the relativistic particles at remotely propagating shock waves.