Do solar decimetric spikes originate in coronal X-ray sources?

TL;DR

This study investigates the spatial relationship between coronal X-ray sources and decimetric radio spikes during solar flares, finding that spikes do not originate from X-ray sources but are linked to higher coronal activity.

Contribution

It provides the first detailed spatial analysis showing that decimetric spikes are not produced at coronal X-ray sources, refining understanding of particle acceleration sites in solar flares.

Findings

Decimetric spikes do not originate from coronal X-ray sources.

A causal link exists between the coronal X-ray source and higher coronal activity.

Radio spikes are spatially separated from X-ray flare sources.

Abstract

In the standard solar flare scenario, a large number of particles are accelerated in the corona. Nonthermal electrons emit both X-rays and radio waves. Thus, correlated signatures of the acceleration process are predicted at both wavelengths, coinciding either close to the footpoints of a magnetic loop or near the coronal X-ray source. We attempt to study the spatial connection between coronal X-ray emission and decimetric radio spikes to determine the site and geometry of the acceleration process. The positions of radio-spike sources and coronal X-ray sources are determined and analyzed in a well-observed limb event. Radio spikes are identified in observations from the Phoenix-2 spectrometer. Data from the Nan\c{c}ay radioheliograph are used to determine the position of the radio spikes. RHESSI images in soft and hard X-ray wavelengths are used to determine the X-ray flare geometry. Those observations are complemented by images from GOES/SXI. We find that decimetric spikes do not originate from coronal X-ray flare sources contrary to previous expectations. However, the observations suggest a causal link between the coronal X-ray source, related to the major energy release site, and simultaneous activity in the higher corona.