staa824.pdf (8.8 MB)
Download file

Magnetohydrodynamic modelling of star-planet interaction and associated auroral radio emission

Download (8.8 MB)
journal contribution
posted on 15.03.2021, 14:07 by Sam Turnpenney, JD Nichols, GA Wynn, X Jia
We present calculations of auroral radio powers of magnetized hot Jupiters orbiting Sun-like stars, computed using global magnetohydrodynamic (MHD) modelling of the magnetospheric and ionospheric convection arising from the interaction between the magnetosphere and the stellar wind. Exoplanetary auroral radio powers are traditionally estimated using empirical or analytically derived relations, such as the radiometric Bode’s law (RBL), which relates radio power to the magnetic or kinetic energy dissipated in the stellar wind–planet interaction. Such methods risk an oversimplification of the magnetospheric electrodynamics giving rise to radio emission. As the next step towards a self-consistent picture, we model the stellar wind–magnetosphere–ionosphere coupling currents using a 3D MHD model. We compute electron-cyclotron maser instability-driven emission from the calculated ionospheric field-aligned current density. We show that the auroral radio power is highly sensitive to interplanetary magnetic field (IMF) strength, and that the emission is saturated for plausible hot Jupiter Pedersen conductances, indicating that radio power may be largely independent of ionospheric conductance. We estimate peak radio powers of 1014 W from a planet exposed to an IMF strength of 103 nT, implying flux densities at a distance of 15 pc from Earth potentially detectable with current and future radio telescopes. We also find a relation between radio power and planetary orbital distance that is broadly consistent with results from previous analytic models of magnetosphere–ionosphere coupling at hot Jupiters, and indicates that the RBL likely overestimates the radio powers by up to two orders of magnitude in the hot Jupiter regime.

History

Citation

Monthly Notices of the Royal Astronomical Society, Volume 494, Issue 4, June 2020, Pages 5044–5055, https://doi.org/10.1093/mnras/staa824

Author affiliation

Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Volume

494

Issue

4

Pagination

5044 - 5055

Publisher

Oxford University Press (OUP) for Royal Astronomical Society

issn

0035-8711

eissn

1365-2966

Acceptance date

19/03/2020

Copyright date

2020

Available date

26/04/2021

Language

English