Work

The Unstable Chromosphere: Predicting Thermal Farley–Buneman Instability Growth Across a Broad Range of Solar Chromospheric Conditions

Year: 2026

Type: article

Abstract: In the coldest regions of the solar atmosphere, models struggle to match observations. Recent work suggests the Thermal Farley–Buneman Instability (TFBI) may play an important role. This meter-scale, electrostatic, collisional, multifluid plasma instability converts energy from neutral flows into turbulent motions and heating. In this work, we improve upon previous methods for solving the linear theory across single-fluid MHD simulation outputs, and present the new tfbi_theory code. We predict much less TFBI growth within a 2D Bifrost plage model than previously suggested. To bypass some limitations of single-fluid MHD models, we also solve TFBI theory across a 5D grid of chromospheric parameters. We find that the TFBI can grow across a wide range of chromospheric densities, temperatures, hydrogen ionization fractions, and magnetic field strengths. We also discover that the minimum ∣ E ∣/∣ B ∣ speed in the neutral reference frame required to drive the TFBI in the chromosphere is less than 3.2 km s −1 in some regions, but always more than 1 km s −1 .

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/ae4ddd

Authors: Samuel Evans, Meers Oppenheim, Juan Martínez-Sykora, Yakov Dimant

Institutions: Boston University, Lockheed Martin (United States), University of Oslo, Lockheed (United States), Search for Extraterrestrial Intelligence

Language: English

Topic: Solar and Space Plasma Dynamics

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $4,499

Funder: National Aeronautics and Space Administration