A burst with double radio spectrum observed up to 212 GHz

TL;DR

This study analyzes a solar flare observed across a broad radio spectrum up to 212 GHz, combining multi-wavelength data to understand particle dynamics and magnetic field evolution during the event.

Contribution

It provides a comprehensive multi-wavelength analysis of a solar flare, including spectral modeling and source localization, extending observations up to 212 GHz.

Findings

Detected radio burst at all frequencies up to 212 GHz

Identified two X-ray sources and a displaced radio source

Observed evolving electron spectral index with soft-hard-soft pattern

Abstract

We study a solar flare that occurred on September 10, 2002, in active region NOAA 10105 starting around 14:52 UT and lasting approximately 5 minutes in the radio range. The event was classified as M2.9 in X-rays and 1N in H\alpha. Solar Submillimeter Telescope observations, in addition to microwave data give us a good spectral coverage between 1.415 and 212 GHz. We combine these data with ultraviolet images, hard and soft X-rays observations and full-disk magnetograms. Images obtained from Ramaty High Energy Solar Spectroscopic Imaging data are used to identify the locations of X-ray sources at different energies and to determine the X-ray spectrum, while ultra violet images allow us to characterize the coronal flaring region. The magnetic field evolution of the active region is analyzed using Michelson Doppler Imager magnetograms. The burst is detected at all available radio-frequencies. X-ray images (between 12 keV and 300 keV) reveal two compact sources and 212 GHz data, used to estimate the radio source position, show a single compact source displaced by 25" from one of the hard X-ray footpoints. We model the radio spectra using two homogeneous sources, and combine this analysis with that of hard X-rays to understand the dynamics of the particles. Relativistic particles, observed at radio wavelengths above 50 GHz, have an electron index evolving with the typical soft-hard-soft behaviour.