Fast magneto-acoustic waves in the solar chromosphere: Comparison of single-fluid and two-fluid approximations

TL;DR

This study compares single-fluid and two-fluid models of magneto-acoustic wave propagation in the solar chromosphere to understand how different approximations affect plasma heating predictions.

Contribution

It provides a detailed comparison of single-fluid and two-fluid models, highlighting the impact of model assumptions on wave energy transport and heating in the partially ionised solar chromosphere.

Findings

The 1F model predicts slightly higher temperature increases than the 2F model.

Wave energy flux is lower in the 2F model, indicating less energy reaches higher layers.

Discrepancies are due to pressure forces and omitted terms in the 1F energy equation.

Abstract

Context: The mechanism behind the heating of the solar chromosphere remains unclear. Friction between neutrals and charges is expected to contribute to plasma heating in a partially ionised plasma (PIP). Aims: We aim to study the efficiency of the frictional heating mechanism in partially ionised plasmas by comparing a single-fluid model (1F) using ambipolar diffusion and a two-fluid model (2F) that incorporates elastic collision terms. Methods: We use the code MANCHA-2F to solve the equations for both models numerically. The simulations involve the vertical propagation of fast magneto-acoustic waves from the top of the photosphere through the chromosphere. The model atmosphere is vertically stratified, including a horizontal, homogeneous magnetic field. We also apply the linear theory to supplement the numerical results. Finally, we look at the assumptions of the 1F model to find out what causes the model discrepancies. Results: The results show that the temperature increase for the 1F model is slightly higher than for the 2F model, especially with long-period waves. The wave energy flux indicates that in the 2F model, the wave is transporting less energy upwards. From the linear theory, we find that the wave in the 2F model loses more energy than in the 1F model in the deep layers, but the opposite occurs in the high layers. Conclusions: The efficient dissipation in the 2F model in deep layers reduces the energy flux at the high layers, reducing heating and explaining the temperature differences between models. We attribute those discrepancies to the contribution of pressure forces to the drift velocity and the omission of a term related to the centre of mass frame reference in the 1F energy equation.}