# Observations of quasi-periodic solar X-ray emission as a result of MHD oscillations in a system of multiple flare loops

## TL;DR

This study analyzes quasi-periodic pulsations in a 2002 solar flare, linking observed X-ray oscillations to MHD wave activity in multiple flare loops, revealing insights into energy release and loop oscillations.

## Contribution

It provides the first detailed interpretation connecting observed QPP in X-ray emissions to MHD oscillations in multiple interacting flare loops.

## Key findings

- Detected two significant QPP periods of 16 and 36 seconds.
- Linked 36-second QPP to MHD oscillations causing energy release.
- Identified 16-second sausage mode oscillations in flare loops.

## Abstract

We investigate the solar flare of 20 October 2002. The flare was accompanied by quasi-periodic pulsations (QPP) of both thermal and nonthermal hard X-ray emissions (HXR) observed by RHESSI in the 3-50 keV energy range. Analysis of the HXR time profiles in different energy channels made with the Lomb periodogram indicates two statistically significant time periods of about 16 and 36 seconds. The 36-second QPP were observed only in the nonthermal HXR emission in the impulsive phase of the flare. The 16-second QPP were more pronounced in the thermal HXR emission and were observed both in the impulsive and in the decay phases of the flare. Imaging analysis of the flare region, the determined time periods of the QPP and the estimated physical parameters of magnetic loops in the flare region allow us to interpret the observations as follows. 1) In the impulsive phase energy was released and electrons were accelerated by successive acts with the average time period of about 36 seconds in different parts of two spatially separated, but interacting loop systems of the flare region. 2) The 36-second periodicity of energy release could be caused by the action of fast MHD oscillations in the loops connecting these flaring sites. 3) During the first explosive acts of energy release the MHD oscillations (most probably the sausage mode) with time period of 16 seconds were excited in one system of the flare loops. 4) These oscillations were maintained by the subsequent explosive acts of energy release in the impulsive phase and were completely damped in the decay phase of the flare.