Heating of the magnetized solar chromosphere by partial ionization effects

TL;DR

This paper investigates how ambipolar diffusion, caused by partial ionization in the magnetized solar chromosphere, significantly enhances current dissipation and contributes to rapid heating, emphasizing its importance in chromospheric models.

Contribution

It demonstrates that ambipolar diffusion can rapidly heat the chromosphere by dissipating magnetic energy, highlighting its crucial role in chromospheric heating models.

Findings

Ambipolar diffusion greatly increases current dissipation in the chromosphere.

Magnetic energy of 10-40 G fields can be efficiently converted into heat.

Numerical simulations confirm rapid heating due to ambipolar effects.

Abstract

In this paper, we study the heating of the magnetized solar chromosphere induced by the large fraction of neutral atoms present in this layer. The presence of neutrals, together with the decrease with height of the collisional coupling, leads to deviations from the classical MHD behavior of the chromospheric plasma. A relative net motion appears between the neutral and ionized components, usually referred to as ambipolar diffusion. The dissipation of currents in the chromosphere is enhanced orders of magnitude due to the action of ambipolar diffusion, as compared to the standard ohmic diffusion. We propose that a significant amount of magnetic energy can be released to the chromosphere just by existing force-free 10--40 G magnetic fields there. As a consequence, we conclude that ambipolar diffusion is an important process that should be included in chromospheric heating models, as it has the potential to rapidly heat the chromosphere. We perform analytical estimations and numerical simulations to prove this idea.