Plasma sloshing in pulse-heated solar and stellar coronal loops

TL;DR

This paper demonstrates that short heat pulses in coronal loops induce large amplitude plasma oscillations, which can serve as diagnostics for flare properties in solar and stellar coronae.

Contribution

It introduces a hydrodynamic modeling approach revealing how heat pulse duration affects plasma oscillations, providing a new diagnostic tool for coronal loop analysis.

Findings

Large amplitude oscillations (~20%) occur when heat pulses are shorter than the sound crossing time.

Oscillation periods are a few minutes, dictated by the sound crossing time in the decay phase.

These oscillations differ from typical MHD waves and can be used to analyze flare dynamics.

Abstract

There is evidence that coronal heating is highly intermittent, and flares are the high energy extreme. The properties of the heat pulses are difficult to constrain. Here hydrodynamic loop modeling shows that several large amplitude oscillations (~ 20% in density) are triggered in flare light curves if the duration of the heat pulse is shorter that the sound crossing time of the flaring loop. The reason is that the plasma has not enough time to reach pressure equilibrium during the heating and traveling pressure fronts develop. The period is a few minutes for typical solar coronal loops, dictated by the sound crossing time in the decay phase. The long period and large amplitude make these oscillations different from typical MHD waves. This diagnostic can be applied both to observations of solar and stellar flares and to future observations of non-flaring loops at high resolution.