Kelvin-Helmholtz instability and Alfvenic vortex shedding in solar eruptions

TL;DR

This study uses 3D MHD simulations to explore Kelvin-Helmholtz instability and Alfvénic vortex shedding in solar eruptions, revealing their specific development locations, observational detectability constraints, and implications for solar physics.

Contribution

It demonstrates the occurrence and spatial dependence of KHI and vortex shedding in solar eruptions through detailed 3D simulations, highlighting observational challenges.

Findings

KHI develops at specific boundary locations depending on magnetic field orientation

Alfvénic vortex shedding occurs in the wake of the eruption

KHI detectability is limited to a narrow viewing angle due to projection effects

Abstract

We report on a three-dimensional MHD numerical experiment of a small scale coronal mass ejection (CME) -like eruption propagating though a non-magnetized solar atmosphere. We find that the Kelvin-Helmholtz instability (KHI) develops at various but specific locations at the boundary layer between the erupting field and the background atmosphere, depending on the relative angle between the velocity and magnetic field. KHI develops at the front and at two of the four sides of the eruption. KHI is suppressed at the other two sides of the eruption. We also find the development of Alfv\'enic vortex shedding flows at the wake of the developing CME due to the 3D geometry of the field. Forward modeling reveals that the observational detectability of the KHI in solar eruptions is confined to a narrow $\approx10^{\circ}$ range when observing off-limb, and therefore its occurrence could be underestimated due to projection effects. The new findings can have significant implications for observations, for heating and for particle acceleration by turbulence from flow-driven instabilities associated with solar eruptions of all scales.