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Magnetic induction processes in hot Jupiters, application to KELT-9b

Dietrich, Wieland and Kumar, Sandeep and Poser, Anna Julia and French, Martin and Redmer, Ronald and Nettelmann, Nadine (2022) Magnetic induction processes in hot Jupiters, application to KELT-9b. Monthly Notices of the Royal Astronomical Society, 517 (3), pp. 3113-3125. Oxford University Press. doi: 10.1093/mnras/stac2849. ISSN 0035-8711.

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Official URL: https://academic.oup.com/mnras/article/517/3/3113/6753224


The small semimajor axes of hot Jupiters lead to high atmospheric temperatures of up to several thousand Kelvin. Under these conditions, thermally ionized metals provide a rich source of charged particles and thus build up a sizeable electrical conductivity. Subsequent electromagnetic effects, such as the induction of electric currents, Ohmic heating, magnetic drag, or the weakening of zonal winds have thus far been considered mainly in the framework of a linear, steady-state model of induction. For hot Jupiters with an equilibrium temperature Teq > 1500 K, the induction of atmospheric magnetic fields is a runaway process that can only be stopped by non-linear feedback. For example, the back-reaction of the magnetic field on to the flow via the Lorentz force or the occurrence of magnetic instabilities. Moreover, we discuss the possibility of self-excited atmospheric dynamos. Our results suggest that the induced atmospheric magnetic fields and electric currents become independent of the electrical conductivity and the internal field, but instead are limited by the planetary rotation rate and wind speed. As an explicit example, we characterize the induction process for the hottest exoplanet, KELT-9b, by calculating the electrical conductivity along atmospheric P-T profiles for the dayside and nightside. Despite the temperature varying between 3000 and 4500 K, the resulting electrical conductivity attains an elevated value of roughly 1 S m-1 throughout the atmosphere. The induced magnetic fields are predominately horizontal and might reach up to a saturation field strength of 400 mT, exceeding the internal field by two orders of magnitude.

Item URL in elib:https://elib.dlr.de/193074/
Document Type:Article
Title:Magnetic induction processes in hot Jupiters, application to KELT-9b
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Dietrich, WielandMax Planck Institute for Solar System Research, D-37077 Goettingen, GermanyUNSPECIFIEDUNSPECIFIED
Kumar, SandeepCenter for Advanced Systems Understanding (CASUS), D-02826 Gorlitz, GermanyUNSPECIFIEDUNSPECIFIED
Poser, Anna JuliaUniversität RostockUNSPECIFIEDUNSPECIFIED
French, MartinInstitut für Physik, Universität Rostock, D-18051 Rostock, GermanyUNSPECIFIEDUNSPECIFIED
Redmer, RonaldUniversität RostockUNSPECIFIEDUNSPECIFIED
Journal or Publication Title:Monthly Notices of the Royal Astronomical Society
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 3113-3125
Publisher:Oxford University Press
Keywords:magnetic fields; plasmas; planets and satellites: atmospheres; planets and satellites: gaseous planets; Astrophysics - Earth and Planetary Astrophysics
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Project PLATO - PMC and Science
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Extrasolar Planets and Atmospheres
Deposited By: Cabrera Perez, Juan
Deposited On:09 Jan 2023 15:19
Last Modified:28 Jun 2023 13:51

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