CORONAS-F observation of gamma-ray emission from the solar flare on 2003 October 29

TL;DR

This study analyzes gamma-ray emissions from the 2003 October 29 solar flare using CORONAS-F and RHESSI data, revealing details about particle acceleration, spectral components, and magnetic restructuring during the flare.

Contribution

It provides a detailed spectral analysis of gamma-ray emissions from a major solar flare, combining data from multiple instruments to understand particle acceleration and magnetic field changes.

Findings

Pion-decay emission observed with a maximum at 20:48-20:51 UT.

Proton spectral index varied over time, reaching a minimum of -3.5 to -3.6.

Temporal correlation between particle acceleration and magnetic restructuring.

Abstract

Appreciable hard X-ray (HXR) and gamma-ray emissions in the 0.04 to 150 MeV energy range associated with the 2003 October 29 solar flare (X10/3B) were observed at 20:38 to 20:58 UT by the SONG instrument onboard the CORONAS-F mission. To restore flare gamma-ray spectra we fitted the SONG energy loss spectra with a three-component model of the incident spectrum: (1) a power law in energy, assumed to be due to electron bremsstrahlung; (2) a broad continuum produced by prompt nuclear de-excitation gamma-lines; and (3) a broad gamma-line generated from pion decay. We also restored spectra from the RHESSI data, compared them with the SONG spectra and found a reasonable agreement between these spectra in the 0.1 to 10 MeV energy range. The pion-decay emission was observed from 20:44:20 UT and had its maximum at 20:48 to 20:51 UT. The power-law spectral index of accelerated protons estimated from the ratio between intensities of different components of gamma rays changed with time. The hardest spectrum with a power-law index S = - 3.5 to - 3.6 was observed at 20:48 to 20:51 UT. Time histories of the pion-decay emission and proton spectrum were compared with changes of the locations of flare energy release as shown by RHESSI hard X-ray images and remote H alpha brightening. An apparent temporal correlation between processes of particle acceleration and restructuring of flare magnetic field was found. In particular, the protons were accelerated to sub-relativistic energies after radical change of the character of footpoint motion from a converging motion to a separation motion.