Coronal magnetic topology and the production of solar impulsive energetic electrons

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.

Exploring the Properties of the Electron Strahl at 1 AU as an Indicator of the Quality of the Magnetic Connection Between the Earth and the Sun

“…Impulsive solar energetic electron (SEE) events at 1 AU are associated with solar x-ray flares, (e.g. Kallenrode and Svestka, 1994;Cliver and Ling, 2007) or near-Sun events (Li et al, 2013) and electrons accelerated near the Sun traveling along the solarwind magnetic field out to a measuring spacecraft at 1 AU. If one can assume that impulsive SEE events are good indicators of magnetic connectivity to the Sun, then examining the strahl intensity during the early times in impulsive SEE events vs. the strahl intensity when SEE events are not seen could be a test of the viability of using the strahl intensity as a gauge of magnetic connectivity to the Sun.…”

“…As can be seen in Figure 4 the strahl intensities for the 216 SEE events are robust in comparison with the black distribution for all times during the years 1998-2013. One might think that the electron strahl should be intense when solar energetic electrons are present because they are two energies out of the same electron distribution function, but that is not the case: the strahl is a representation of the coronal electron temperature (Bercic et al, 2020;Boldyrev et al, 2020) and the solar energetic electrons are produced by specific temporal acceleration processes (Kallenrode and Svestka, 1994;Cliver and Ling, 2007;Li et al, 2013). Also, for the early times of impulsive SSE events, the 272 eV electrons of the observed strahl at 1 AU left the Sun more than 4.3 h before the flare occurred.…”

A substorm-associated enhancement in the XUV radiation measuring channel observed by ESP/EVE/SDO

“…A reasonable explanation may be that they are energetic electrons. Still, they are not energetic electrons accelerated by an impulsive solar event, because the two active regions do not seem to be consistent with the coronal magnetic topology that Li et al (2013) proposed.…”