Coronal magnetic topology and the production of solar impulsive energetic electrons

¹ School of Astronomy and Space Science, Nanjing University, 210093 Nanjing, PR China
e-mail: lic@nju.edu.cn
² Key Laboratory for Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, 210093 Nanjing, PR China
³ Key Laboratory of Solar Activity, The National Astronomical Observatories, CAS, 20A Datun Road, Chaoyang District, 100012 Beijing, PR China

Received: 13 June 2013
Accepted: 10 July 2013

Abstract

We investigate two candidate solar sources or active regions (ARs) in association with a solar impulsive energetic electron (SIEE) event on 2002 October 20. The solar particle release (SPR) times of SIEEs are derived by using their velocity dispersion with consideration of the instrumental effect. It is found that there are double electron injections at the Sun. The low-energy (≲13 keV) electron injection coincides with a C6.6 flare in AR10154 and is accompanied with prominent type III radio bursts rather than a stronger M1.8 flare in AR10160. The M1.8 flare produces, however, faint type III radio bursts. Electrons of  ~25 to  ~300 keV are released  ~9 min later when a jet-like CME travels to  ~2.6 solar radii. We further examine the coronal magnetic configurations above the two ARs based on the potential field source surface (PFSS) model. It is found that open field lines, rooted in AR10154 and well connected to the Earth, provide escaping channels for energetic electrons. Only a small portion of magnetic fields are opened above AR10160, being responsible for the faint type III radio bursts. These lines are, however, not well connected, making it impossible for SIEEs detection by near-Earth spacecraft. The results appear to establish a physical link between coronal magnetic topology, formation of type III radio bursts, and production of SIEEs.