Kelvin-Helmholtz instability of a coronal streamer

TL;DR

This paper reports the first observation of a kink-like oscillation in a coronal streamer caused by Kelvin-Helmholtz instability, revealing insights into energy transfer processes in solar plasma through detailed LASCO observations.

Contribution

It provides the first observational evidence linking Kelvin-Helmholtz instability to coronal streamer oscillations using LASCO data.

Findings

Wave period of 70-80 minutes observed.

Wavelength increased from 2 to 3 solar radii over 1.5 hours.

Phase speed decreased from 406 to 356 km/s during the event.

Abstract

The shear-flow-driven instability can play an important role in energy transfer processes in coronal plasma. We present for the first time the observation of a kink-like oscillation of a streamer probably caused by the streaming kinkmode Kelvin-Helmholtz instability. The wave-like behavior of the streamer was observed by Large Angle and Spectrometric Coronagraph Experiment (LASCO) C2 and C3 aboard SOlar and Heliospheric Observatory (SOHO). The observed wave had a period of about 70 to 80 minutes, and its wavelength increased from 2 Rsun to 3 Rsun in about 1.5 hours. The phase speeds of its crests and troughs decreased from 406 \pm 20 to 356 \pm 31kms^{-1} during the event. Within the same heliocentric range, the wave amplitude also appeared to increase with time. We attribute the phenomena to the MHD Kelvin-Helmholtz instability which occur at a neutral sheet in a fluid wake. The free energy driving the instability is supplied by the sheared flow and sheared magnetic field across the streamer plane. The plasma properties of the local environment of the streamer were estimated from the phase speed and instability threshold criteria.