Lookup NU author(s): Alexander Hindle,
Dr Paul Bushby,
Professor Tamara Rogers
This is the authors' accepted manuscript of an article that has been published in its final definitive form by Institute of Physics, 2019.
For re-use rights please refer to the publisher's terms and conditions.
Westward winds have now been inferred for two hot Jupiters: HAT-P-7b and CoRoT-2b. Such observations could be the result of a number of physical phenomena such as cloud asymmetries, asynchronous rotation or magnetic fields. For the hotter hot Jupiters magnetic fields are an obvious candidate, though the actual physical mechanism remains poorly understood. Here we show that a strong toroidal magnetic field causes the planetary-scale equatorial magneto-Kelvin wave to structurally shear as it travels, resulting in westward tilting eddies, which drive a reversal of the equatorial winds from their eastward hydrodynamic counterparts. Using our simplified model we estimate that the equatorial winds of HAT-P-7b would reverse for a planetary dipole field strength Bdip,HAT-P-7b > 6G, a result that is consistent with three-dimensional magnetohydrodynamic simulations and lies below typical surface dipole estimates of inflated hot Jupiters. The same analysis suggests that the minimum dipole field strength required to reverse the winds of CoRoT-2b is Bdip,CoRoT-2b > 3kG, which considerably exceeds estimates of the maximum surface dipole strength for hot Jupiters. We hence conclude that our magnetic wave-driven mechanism provides an explanation for wind reversals on HAT-P-7b, however other physical phenomena provide more plausible explanations for wind reversals on CoRoT-2b.
Author(s): Hindle AW, Bushby PJ, Rogers TM
Publication type: Article
Publication status: Published
Journal: The Astrophysical Journal Letters
Online publication date: 21/02/2019
Acceptance date: 10/02/2019
Date deposited: 11/02/2019
ISSN (print): 2041-8205
ISSN (electronic): 2041-8213
Publisher: Institute of Physics
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