A Study on Red Asymmetry of H-alpha Flare Ribbons Using Narrowband Filtergram in the 2001 April 10 Solar Flare

TL;DR

This study investigates the red asymmetry of H-alpha emission during a solar flare, revealing its spatial distribution, temporal behavior, and relation to energy release regions using narrowband filtergram data.

Contribution

It provides detailed observations of red asymmetry in flare ribbons, highlighting its location on outer edges and its independence from kernel intensity, offering new insights into chromospheric dynamics.

Findings

Red asymmetry appears all over flare ribbons.

Strong red asymmetry is located on outer edges of ribbons.

Peak asymmetry is not strongly dependent on kernel intensity.

Abstract

We report a detailed examination of the "red asymmetry" of H-alpha emission line seen during the 2001 April 10 solar flare by using a narrowband filtergram. We investigated the temporal evolution and the spatial distribution of the red asymmetry by using the H-alpha data taken with the 60cm Domeless Solar Telescope at Hida Observatory, Kyoto University. We confirmed that the red asymmetry clearly appeared all over the flare ribbons, and the strong red asymmetry is located on the outer narrow edges of the flare ribbons, with the width of about 1.5" - 3.0" (1000 - 2000 km), where the strong energy releases occur. Moreover, we found that the red asymmetry, which also gives a measure of the Doppler shift of the H-alpha emission line concentrates on a certain value, not depending on the intensity of the H-alpha kernels. This implies not only that the temporal evolutions of the red asymmetry and those of the intensity are not in synchronous in each flare kernel, but also that the peak asymmetry (or velocity of the chromospheric condensation) of individual kernel is not a strong function of their peak intensity.