Kelvin-Helmholtz instability in coronal mass ejections and solar surges

Abstract

In this article, we study the Kelvin-Helmholtz (KH) instability of magnetohydrodynamic (MHD) waves propagating in the solar atmosphere. The main focus is on the modeling the KH instability development in coronal mass ejections (CMEs) and solar surges in view of its (instability) contribution to triggering a wave turbulence subsequently leading to an effective coronal heating. KH instability of MHD waves in coronal active regions recently observed and imaged in unprecedented detail in EUV thanks to the high cadence, high-resolution observations by SDO/AIA instrument, and spectroscopic observations by Hinode/EIS instrument is a challenge for modeling these events. It is shown that considering the solar mass flows of coronal mass ejections as moving cylindrical twisted magnetic flux tubes the imaged instability can be explained in terms of unstable m =-3 MHD mode. Obtained critical jet speeds for the instability onset as well as the linear wave growth rates are in good agreement with observational data. Alongside the KH instability in CMEs, we study also the conditions for the instability onset in solar surges. It is obtained that MHD high-mode harmonics propagating along such jets might become unstable against KH instability at critical jets' velocities accessible for surges. © 2016 AIP Publishing LLC.