More than mass proportional heating of heavy ions by supercritical collisionless shocks in the solar corona

TL;DR

This paper introduces a model where small-scale supercritical collisionless shocks in the solar corona cause heavy ions to be heated more than protons, explaining observed temperature ratios.

Contribution

The paper presents a novel model linking shock wave interactions to heavy ion heating in the solar corona, aligning with observational data.

Findings

Heavy ions are heated more than protons by shock reflection and acceleration.

The model reproduces observed temperature ratios of ions in the corona and solar wind.

Ion acceleration occurs perpendicular to magnetic fields, consistent with observations.

Abstract

We propose a new model for explaining the observations of more than mass proportional heating of heavy ions in the polar solar corona. We point out that a large number of small scale intermittent shock waves can be present in the solar corona. The energization mechanism is, essentially, the ion reflection off supercritical quasi-perpendicular collisionless shocks in the corona and the subsequent acceleration by the motional electric field ${\bf E} = - (1/c) {\bf V} \times {\bf B}$. The acceleration due to ${\bf E}$ is perpendicular to the magnetic field, in agreement with observations, and is more than mass proportional with respect to protons, because the heavy ion orbit is mostly upstream of the quasi-perpendicular shock foot. The observed temperature ratios between O$^{5+}$ ions and protons in the polar corona, and between $\alpha$ particles and protons in the solar wind are easily recovered.