Solar radio burst associated with the falling bright EUV blob

TL;DR

This study reports a rare solar radio burst linked to a falling bright EUV blob, suggesting it is generated by a thermal conduction front caused by the blob's interaction with the chromosphere.

Contribution

It provides the first detailed observation connecting a slowly positively drifting radio burst with a falling EUV blob and proposes a new generation mechanism involving thermal conduction fronts.

Findings

The radio burst was associated with a falling bright EUV blob.

The blob interacted with the chromosphere, affecting H alpha spectra.

The proposed mechanism involves thermal conduction front formation.

Abstract

At the beginning of the 4 November 2015 flare, in the 1300 -- 2000 MHz frequency range, we observed a very rare slowly positively drifting burst. We searched for associated phenomena in simultaneous EUV observations made by IRIS, SDO/AIA, Hinode/XRT and in H alpha observations. We found that this radio burst was accompanied with the bright blob, visible at transition region, coronal, and flare temperatures, falling down to the chromosphere along the dark loop with the velocity of about 280 km/s. The dark loop was visible in H alpha but disappeared afterwards. Furthermore, we found that the falling blob interacted with the chromosphere as expressed by a sudden change of the H alpha spectra at the location of this interaction. Considering different possibilities we propose that the observed slowly positively drifting burst is generated by the thermal conduction front formed in front of the falling hot EUV blob.