Energy and spectral analysis of confined solar flares from radio and X-ray observations

TL;DR

This study analyzes the energy and spectral properties of confined solar flares using radio and X-ray data, revealing that microwave burst characteristics can estimate flare power and that confined flares have stronger magnetic fields but less high-energy electron acceleration.

Contribution

It provides new insights into the spectral behavior and energy emission of confined solar flares, highlighting the relationship between microwave properties and flare strength.

Findings

Confined flares show microwave bursts extending to 9.4-15.4 GHz.

Peak microwave frequencies are between 4.995 GHz and 17 GHz.

Microwave energy and peak frequency can estimate flare power.

Abstract

The energy and spectral shape of radio bursts may help us understand the generation mechanism of solar eruptions, including solar flares, CMEs, eruptive filaments, and various scales of jets. The different kinds of flares may have different characteristics of energy and spectral distribution. In this work, we selected 10 mostly confined flare events during October 2014 to investigate their overall spectral behavior and the energy emitted in microwaves by using radio observations from microwaves to interplanetary radio waves, and X-ray observations of GOES, RHESSI, and Fermi/GBM. We found that: All the confined flare events were associated with a microwave continuum burst extending to frequencies of 9.4 - 15.4 GHz, and the peak frequencies of all confined flare events are higher than 4.995 GHz and lower than or equal to 17 GHz. The median value is around 9 GHz. The microwave burst energy (or fluence) as well as the peak frequency are found to provide useful criteria to estimate the power of solar flares. The observations imply that the magnetic field in confined flares tends to be stronger than that in 412 flares studied by Nita et al. 2004. All 10 events studied did not produce detectable hard X-rays with energies above 300 keV indicating the lack of efficient acceleration of electrons to high energies in the confined flares.