Can Auroral Heating Explain Brown Dwarf Thermal Inversions?

Abstract

Recent modeling of the JWST spectra of the Y-dwarf CWISEPJ193518.59-154620.3 (Faherty et al. 2024; Suárez et al. 2025) and the T-dwarf SIMPJ013656.5+093347.3 (Nasedkin et al. 2025) indicates the presence of a thermal inversion in their atmospheres, implying an additional source of heating. Auroral energy deposition has been proposed as a potential mechanism. In this work, we model auroral energy deposition processes and the resulting atmospheric response to assess whether physically motivated auroral electron beam energy spectra can reproduce the inferred thermal inversions. We simulate the effects of several auroral electron beam energy spectra consistent with observations of the Jovian population of auroral electrons and scale them to the total electron flux expected for brown dwarfs. We find that auroral energy deposition alone cannot reproduce both the magnitude and pressure level of the inferred inversion in either object. While inversions are produced in our models, they occur at pressures that are too low compared to those required by the observations. These results suggest that the actual population of auroral electrons includes a stronger high-energy component than considered here, that additional heating mechanisms contribute to the observed thermal inversions, and/or that heterogeneous heating of the atmosphere is important for determining the observed emission.