Linear analysis of shear-flow instabilities in a prominence-corona interface with ambipolar diffusion

TL;DR

This paper investigates how partial ionization and ambipolar diffusion influence the Kelvin-Helmholtz instability at prominence-corona interfaces, revealing that ambipolar diffusion generally destabilizes the flow and lowers the velocity threshold for instability.

Contribution

It provides a linear analysis of shear-flow instabilities considering ambipolar diffusion in a partially ionized prominence plasma, which is a novel approach.

Findings

Ambipolar diffusion reduces the flow velocity threshold for KHi onset.

Compressibility and gas pressure significantly affect instability in sub-Alfvénic flows.

Ambipolar diffusion has a destabilizing effect on the interface.

Abstract

Observations have shown the presence of the Kelvin-Helmholtz instability (KHi) in solar prominences. Effects due to partial ionization of the prominence plasma may influence the KHi onset. We study the triggering of the KHi in an interface model that consists of a partially ionized prominence region and a fully ionized coronal region, with a uniform magnetic field parallel to the interface. There is a longitudinal flow in the prominence region. The plasma is compressible and the role of ambipolar diffusion, which accounts for collisions between charges and neutrals, is taken into account in the prominence plasma. We derive the dispersion relation of linear perturbations on the interface and analyze some limit cases analytically. Numerical results are obtained for realistic prominence parameters. We find that compressibility and gas pressure are important in determining the unstable flow velocities, specially in the range of sub-Alfv\'enic flows that are consistent with the observations. The ambipolar diffusion has a generally destabilizing influence and reduces the threshold flow velocity for the KHi onset.