Simulations of chromospheric heating by ambipolar diffusion

TL;DR

This paper introduces a mechanism based on ambipolar diffusion involving neutral atoms and magnetic fields that could efficiently heat the solar chromosphere by dissipating currents, potentially balancing radiative losses.

Contribution

It demonstrates that ambipolar diffusion can significantly enhance current dissipation, providing a plausible heating mechanism for the solar chromosphere.

Findings

Ambipolar diffusion increases current dissipation in the chromosphere.

The energy released can offset radiative losses.

Heating occurs on timescales of seconds to minutes.

Abstract

We propose a mechanism for efficient heating of the solar chromosphere, based on non-ideal plasma effects. Three ingredients are needed for the work of this mechanism: (1) presence of neutral atoms; (2) presence of a non-potential magnetic field; (3) decrease of the collisional coupling of the plasma. Due to decrease of collisional coupling, a net relative motion appears between the neutral and ionized components, usually referred to as "ambipolar diffusion". This results in a significant enhancement of current dissipation as compared to the classical MHD case. We propose that the current dissipation in this situation is able to provide enough energy to heat the chromosphere by several kK on the time scale of minutes, or even seconds. In this paper, we show that this energy supply might be sufficient to balance the radiative energy losses of the chromosphere.