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Stellar wind-magnetosphere interaction at exoplanets: Computations of auroral radio powers

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journal contribution
posted on 17.11.2016, 12:02 by J. D. Nichols, S. E. Milan
We present calculations of the auroral radio powers expected from exoplanets with magnetospheresdriven by an Earth-like magnetospheric interaction with the solar wind. Specifically,we compute the twin cell-vortical ionospheric flows, currents, and resulting radio powers resultingfrom a Dungey cycle process driven by dayside and nightside magnetic reconnection,as a function of planetary orbital distance and magnetic field strength.We include saturation ofthe magnetospheric convection, as observed at the terrestrial magnetosphere, and we presentpower-law approximations for the convection potentials, radio powers and spectral flux densities.We specifically consider a solar-age system and a young (1 Gyr) system. We showthat the radio power increases with magnetic field strength for magnetospheres with saturatedconvection potential, and broadly decreases with increasing orbital distance.We show that themagnetospheric convection at hot Jupiters will be saturated, and thus unable to dissipate thefull available incident Poynting flux, such that the magnetic Radiometric Bode's Law (RBL)presents a substantial overestimation of the radio powers for hot Jupiters. Our radio powersfor hot Jupiters are ∼5-1300 TW for hot Jupiters with field strengths of 0.1-10 BJ orbitinga Sun-like star, while we find that competing effects yield essentially identical powers forhot Jupiters orbiting a young Sun-like star. However, in particular, for planets with weakermagnetic fields, our powers are higher at larger orbital distances than given by the RBL, andthere are many configurations of planet that are expected to be detectable using SKA.

Funding

JDN was supported by an STFC Advanced Fellowship (ST/I004084/1). SEM was supported by STFC Grant ST/K001000/1.

History

Citation

Monthly Notices of the Royal Astronomical Society, 461, 2353–2366 (2016)

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Publisher

Oxford University Press (OUP), Royal Astronomical Society

issn

0035-8711

eissn

1365-2966

Acceptance date

13/06/2016

Copyright date

2016

Available date

17/11/2016

Publisher version

http://mnras.oxfordjournals.org/content/461/3/2353

Language

en