Broadband Quasi-Periodic Radio and X-ray Pulsations in a Solar Flare

TL;DR

This study analyzes microwave and X-ray pulsations in a solar flare, using Fourier analysis to compare models of MHD oscillations versus electron injection, concluding electron injection is the more likely cause.

Contribution

It provides the first detailed comparison of observed pulsation properties with two models, favoring electron injection as the primary mechanism for quasiperiodic oscillations.

Findings

Quasiperiodic electron injection explains observed pulsations better than MHD oscillations.

Radio and X-ray oscillations are linked to particle acceleration processes.

The study offers insights into particle transport during solar flares.

Abstract

We describe microwave and hard X-ray observations of strong quasiperiodic pulsations from the GOES X1.3 solar flare on 15 June 2003. The radio observations were made jointly by the Owens Valley Solar Array (OVSA), the Nobeyama Polarimeter (NoRP), and the Nobeyama Radioheliograph (NoRH). Hard X-ray observations were made by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Using Fourier analysis, we study the frequency- and energy-dependent oscillation periods, differential phase, and modulation amplitudes of the radio and X-ray pulsations. Focusing on the more complete radio observations, we also examine the modulation of the degree of circular polarization and of the radio spectral index. The observed properties of the oscillations are compared with those derived from two simple models for the radio emission. In particular, we explicitly fit the observed modulation amplitude data to the two competing models. The first model considers the effects of MHD oscillations on the radio emission. The second model considers the quasi-periodic injection of fast electrons. We demonstrate that quasiperiodic acceleration and injection of fast electrons is the more likely cause of the quasiperiodic oscillations observed in the radio and hard X-ray emission, which has important implications for particle acceleration and transport in the flaring sources.