Volcanic Satellites and Ion Escape in the Magnetospheres of Ultra-Cool and Brown Dwarf Stars
Abstract
Radio emissions at gigahertz frequencies of ultra-cool dwarf and brown dwarf stars suggest the presence of radiation belts not unlike Jupiter's. We investigate the possibility that the inferred magnetospheric plasma at the primary star is sourced by an active planet or via ion escape modeled as a weak ionospheric outflow. We consider indirect methods to estimate the magnetospheric plasma mass flow from auroral radio emission and apply them to the ultra-cool dwarf LSR J1835+3259. We find that an ionospheric outflow on the order of 105 kg s−1 is a viable source if the ionospheric effective Pedersen conductance is lower than ∼ 0.003 mho. On the other hand, a tidally-heated volcanic satellite with the same mass and radius as Io and an orbit with a semimajor axis lower than about $10$ stellar radii, whose eccentricity (e ∼ 10−3) is maintained by perturbations by other planets in the system, is found to be a viable source of magnetospheric plasma without strong limitations on the ionospheric conductance. The volcanic satellite scenario is also naturally in sync with the recent finding that ultra-cool dwarfs with distant substellar or stellar companions are remarkably more likely to be detected as radio emitters.
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BibTeX
@misc{lanza2026volcanic,
title = {{Volcanic Satellites and Ion Escape in the Magnetospheres of Ultra-Cool and Brown Dwarf Stars}},
author = {A. F. Lanza and A. V. Oza},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.25964},
eprint = {2607.25964},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.25964},
}
RIS
TY - UNPB
TI - Volcanic Satellites and Ion Escape in the Magnetospheres of Ultra-Cool and Brown Dwarf Stars
AU - A. F. Lanza
AU - A. V. Oza
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2607.25964
UR - https://arxiv.org/abs/2607.25964
AB - Radio emissions at gigahertz frequencies of ultra-cool dwarf and brown dwarf stars suggest the presence of radiation belts not unlike Jupiter's. We investigate the possibility that the inferred magnetospheric plasma at the primary star is sourced by an active planet or via ion escape modeled as a weak ionospheric outflow. We consider indirect methods to estimate the magnetospheric plasma mass flow from auroral radio emission and apply them to the ultra-cool dwarf LSR J1835+3259. We find that an ionospheric outflow on the order of 10^5 kg s^−1 is a viable source if the ionospheric effective Pedersen conductance is lower than ∼ 0.003 mho. On the other hand, a tidally-heated volcanic satellite with the same mass and radius as Io and an orbit with a semimajor axis lower than about $10$ stellar radii, whose eccentricity (e ∼ 10^−3) is maintained by perturbations by other planets in the system, is found to be a viable source of magnetospheric plasma without strong limitations on the ionospheric conductance. The volcanic satellite scenario is also naturally in sync with the recent finding that ultra-cool dwarfs with distant substellar or stellar companions are remarkably more likely to be detected as radio emitters.
ER -