Energy Release and Initiation of Sunquake in C-class Flare

TL;DR

This study analyzes a rare C-class solar flare that produced a sunquake, exploring the mechanisms behind this phenomenon using multi-instrument data, and suggests that rapid current changes, rather than high-energy electrons, likely initiate the sunquake.

Contribution

It provides the first detailed analysis of a weak C-class flare generating a sunquake, highlighting the role of electric currents over energetic electrons in sunquake initiation.

Findings

The sunquake was caused by a compact photospheric impact unrelated to the strongest HXR source.

A rapid increase in electric currents correlates with the flare energy release.

Sunquake initiation may be linked to current dissipation or Lorentz force, not high-energy electrons.

Abstract

We present analysis of C7.0 solar flare of Febrary 17, 2013, revealing a strong helioseismic response (sunquake) caused by a very compact impact in the photosphere. This is the weakest known C-class flare generating a sunquake event. To investigate possible mechanisms of this event, and to understand the role of accelerated charged particles and photospheric electric currents, we use data from three space observatories: Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Solar Dynamics Observatory (SDO) and Geostationary Operational Environmental Satellite (GOES). We find that the photospheric flare impact does not spatially correspond to the strongest HXR emission source, but both of these events are parts of the same energy release. Our analysis reveals a close association of the flare energy release with a rapid increase of the electric currents, and suggests that the sunquake initiation is unlikely to be explained by the impact of high-energy electrons but may be associated with a rapid current dissipation or a localized impulsive Lorentz force.