Multi-fluid Simulation of Solar Chromospheric Turbulence and Heating Due to the Thermal Farley-Buneman Instability

TL;DR

This paper introduces the Thermal Farley-Buneman instability (TFBI) as a key process causing turbulence and heating in the Sun's chromosphere, using multi-fluid simulations to match theoretical predictions and explain observational discrepancies.

Contribution

First multi-fluid simulation of the TFBI, demonstrating its development, turbulence, and heating effects in the solar chromosphere, bridging theory and observations.

Findings

TFBI develops in cold chromospheric regions

Simulation results agree with linear theory

TFBI-driven turbulence contributes to heating

Abstract

Models fail to reproduce observations of the coldest parts of the Sun's atmosphere, where interactions between multiple ionized and neutral species prevent an accurate MHD representation. This paper argues that a meter-scale electrostatic plasma instability develops in these regions and causes heating. We refer to this instability as the Thermal Farley-Buneman instability, or TFBI. Using parameters from a 2.5D radiative MHD Bifrost simulation, we show that the TFBI develops in many of the colder regions in the chromosphere. This paper also presents the first multi-fluid simulation of the TFBI and validates this new result by demonstrating close agreement with theory during the linear regime. The simulation eventually develops turbulence, and we characterize the resulting wave-driven heating, plasma transport, and random motions. These results all contend that effects of the TFBI contribute to the discrepancies between solar observations and radiative MHD models.