Analysis of intermittency in submillimeter radio and hard X-Rays during the impulsive phase of a solar flare

TL;DR

This study analyzes intermittency in solar flare emissions in hard X-rays and submillimeter radio data, revealing different energy release processes and acceleration mechanisms during the impulsive phase.

Contribution

It introduces a cross-wavelet based method to identify and compare intermittency signatures in multi-wavelength solar flare data, highlighting distinct behaviors at different scales.

Findings

Submillimeter data shows cascade and avalanche processes at different scales.

Hard X-ray data indicates cascade processes dominate above 10 seconds.

Different acceleration mechanisms are responsible for electrons at different energies.

Abstract

We present an analysis of intermittent processes occurred during the impulsive phase of the flare SOL2012-03-13, using hard X-rays and submillimeter radio data. Intermittency is a key characteristic in turbulent plasmas and have been a analyzed recently for hard X-rays data only. Since in a typical flare the same accelerated electron population is believed to produce both hard X-rays and gyrosynchrotron, we compare both time profiles searching for intermittency signatures. For that we define a cross-wavelet power spectrum, that is used to obtain the Local Intermittency Measure or LIM. When greater than three, the square LIM coefficients indicate a local intermittent process. The LIM$^2$ coefficient distribution in time and scale helps to identify avalanche or cascade energy release processes. We find two different and well separated intermittent behaviors in the submillimeter data: for scales greater than 20 s, a broad distribution during the rising and maximum phases of the emission seems to favor a cascade process; for scales below 1 s, short pulses centered on the peak time, are representative of avalanches. When applying the same analysis to hard X-rays, we find only the scales above 10 s producing a distribution related to a cascade energy fragmentation. Our results suggest that different acceleration mechanisms are responsible for tens of keV and MeV energy ranges of electrons.