Flare processes evolution and polarization changes of fine structures of solar radio emission in the April 11, 2013 event

TL;DR

This study analyzes the evolution and polarization changes of fine structures in solar radio emissions during the April 11, 2013 flare, combining multi-instrument observations to understand their source regions and emission modes.

Contribution

It provides a multi-instrument analysis of fine structures and polarization dynamics in solar radio emissions, linking them to flare activity and magnetic field configurations.

Findings

Zebra patterns correspond to the ordinary radio emission mode.

Fine structures are associated with flare brightening at loop tops.

Polarization dynamics relate to flare exciter motion.

Abstract

The measurement of positions and sizes of radio sources in the observations of solar radio spectral fine structures in an M6.5 flare on April 11, 2013 were observed simultaneously by several radio instruments at four different observatories: Chinese Solar Broadband Radio Spectrometers at Huairou (SBRS/Huairou), Ondrejov Radio spectrograph in the Czech Republic (ORSC/Ondrejov), Badary Broadband Microwave spectropolarimeter (BMS/Irkutsk), and spectrograph/IZMIRAN (Moscow, Troitsk). The fine structures include microwave zebra patterns (ZP), fast pulsations, and fibers. They were observed during the flare brightening located at the tops of a loop arcade. The dynamics of the polarization was associated with the motion of the flare exciter, which was observed in EUV images at 171A and 131A (SDO/AIA). Combining magnetograms observed by the SDO Helioseismic and Magnetic Imager (HMI) with the homologous assumption of EUV flare brightening and ZP bursts, we deduced that the observed ZPs correspond to the ordinary radio emission mode. However, future analysis needs to verify the assumption that zebra radio sources are really related to a closed magnetic loop, and are located at lower heights in the solar atmosphere than the source of pulsations.