Modeling of gyrosynchrotron radio emission pulsations produced by MHD loop oscillations in solar flares

TL;DR

This study models how different MHD oscillation modes in solar flare loops affect radio emissions, enabling identification of specific oscillation modes through analysis of radio signatures and applying this to real solar flare data.

Contribution

It introduces a quantitative method to distinguish MHD oscillation modes in solar flares by analyzing radio emission signatures, validated with observational data.

Findings

Detected possible sausage mode oscillation in a solar flare.

Identified kink or torsional oscillations in another flare.

Developed a technique to differentiate MHD modes using radio signatures.

Abstract

A quantitative study of the observable radio signatures of the sausage, kink, and torsional MHD oscillation modes in flaring coronal loops is performed. Considering first non-zero order effect of these various MHD oscillation modes on the radio source parameters such as magnetic field, line of sight, plasma density and temperature, electron distribution function, and the source dimensions, we compute time dependent radio emission (spectra and light curves). The radio light curves (of both flux density and degree of polarization) at all considered radio frequencies are than quantified in both time domain (via computation of the full modulation amplitude as a function of frequency) and in Fourier domain (oscillation spectra, phases, and partial modulation amplitude) to form the signatures specific to a particular oscillation mode and/or source parameter regime. We found that the parameter regime and the involved MHD mode can indeed be distinguished using the quantitative measures derived in the modeling. We apply the developed approach to analyze radio burst recorded by Owens Valley Solar Array and report possible detection of the sausage mode oscillation in one (partly occulted) flare and kink or torsional oscillations in another flare.