Oscillatory processes in solar flares

TL;DR

This paper discusses the nature of quasi-periodic pulsations in solar flares, linking them to MHD processes and demonstrating the effectiveness of Empirical Mode Decomposition for analyzing these oscillations.

Contribution

It introduces the application of Empirical Mode Decomposition to analyze nonlinear, non-stationary MHD oscillations in solar flare emissions.

Findings

QPP are linked to MHD auto-oscillations.

Numerical simulations show spontaneous and induced oscillatory regimes.

Empirical Mode Decomposition effectively analyzes complex oscillations.

Abstract

Electromagnetic (radio, visible-light, UV, EUV, X-ray and gamma-ray) emission generated by solar and stellar flares often contains pronounced quasi-periodic pulsations (QPP). Physical mechanisms responsible for the generation of long-period QPP (with the periods longer than one second) are likely to be associated with MHD processes. The observed modulation depths, periods and anharmonicity of QPP suggest that they can be linked with some kind of MHD auto-oscillations, e.g. an oscillatory regime of magnetic reconnection. Such regimes, of both spontaneous and induced nature, have been observed in resistive-MHD numerical simulations. The oscillations are essentially nonlinear and non-stationary. We demonstrate that a promising novel method for their analysis is the Empirical Mode Decomposition technique.