Slow Magnetoacoustic Waves in Two-Ribbon Flares

Introduction

The understanding of three-dimensional morphology and dynamics of large, eruptive, two-ribbon flares can shed light on the physical processes operating in solar energy releases, which are still under very active scrutiny. According to the more or less standard model of eruptive flares oppositely directed magnetic field lines being in the form of arcade of magnetic loops are stretched by some non-stationary agent (e.g. by an erupting twisted magnetic flux rope or filament) to form a quasi-vertical current sheet in the corona. Here, in the current sheet, magnetic field lines can reconnect converting free magnetic energy to thermal and kinetic energy of plasma and charged particles causing a multitude of secondary flaring effects.

Unfortunately, the standard model is essentially two-dimensional. Being capable to explain a lot of observational flare effects in the plane perpendicular to the magnetic neutral line and flare arcade axis, it does not predict flare development in the third dimension - along the neutral line.

Nevertheless, in a number of observations energy release is seen to propagate along the axis of the flaring arcade, parallel to the magnetic neutral line.