Accelerated Electron Propagation Model for the Flare Arcade of the September 23, 2014, Event from RHESSI, SDO, and Nobeyama Radioheliograph Observations

Abstract

A multi-wavelength study and simulation is conducted for the solar flare SOL2014-09-23T23:11. GOES-class M2.5. Radio (Nobeyama Radioheliograph) and X-ray (Reuven Ramaty High Energy Solar Spectroscopic Imager) maps and energy spectra are studied, including their temporal and spatial evolution, with the superposition of radiation sources on the magnetic field structure. For the first time, a simulation of accelerated electrons transport in several characteristic magnetic structures of a flare arcade simultaneously is conducted. Accelerated electron injection functions, which depend on the space along the magnetic loop, pitch angle, and energy, are fitted to reconcile observations with the simulation results such that the calculated radiation parameters are consistent with the observed brightness distributions of hard X‑rays in the range of 28–135 keV and gyrosynchrotron radiation of 17 and 35 GHz. The energy spectrum of the electron beam corresponds in this case to one- and two-power law functions with spectral indices in the ranges δ₁ ≈ 4–5 and δ₂ ≈ 2.0–2.4 and spectrum break energy E_br ≈ 240–320 keV, depending on the specific magnetic structure. The pitch-angle distribution of accelerated electrons is essentially an anisotropic electron flux with an divergence angle of ~80° from the magnetic looptops towards the footpoint with a dominant hard X-ray source.