The effect of including field‐aligned potentials in the coupling between Jupiter's thermosphere, ionosphere, and magnetosphere

Abstract

Jupiter's magnetosphere‐ionosphere‐thermosphere system drives the brightest, steadiest aurora in our solar system. This emission is the result of an electrical current system, which couples the magnetosphere to the planetary atmosphere in an attempt to enforce the corotation of the middle magnetospheric plasma. Field‐aligned currents transfer angular momentum from the atmosphere to the magnetosphere. In the equatorial plane, the field‐aligned currents diverge into radially outward currents, which exert a torque on the plasma due to the J × B forces. Equatorward ionospheric currents exert an opposite torque on the ionosphere, which interacts with the thermosphere via ion‐neutral collisions. The upward field‐aligned currents result in auroral electron precipitation, depositing energy into the high‐latitude atmosphere. This energy input is a possible candidate for explaining the large thermospheric temperature measured by the Galileo probe at equatorial latitudes; however, previous atmospheric circulation models have shown that the bulk of the energy is transported poleward, rather than equatorward. We present numerical results of Jupiter's coupled magnetosphere‐ionosphere‐thermosphere system including, for the first time, field‐aligned potentials. The model is compared with three previously published works. We find that the rotational decoupling of the magnetospheric and thermospheric angular velocities in the presence of field‐aligned potentials tempers the thermospheric response to the outward transport of magnetospheric plasma, but this is a secondary effect to variations in the Pedersen conductance.

Magnetosphere‐Ionosphere‐Thermosphere Coupling at Jupiter Using a Three‐Dimensional Atmospheric General Circulation Model

“…T is the weighted average of all the horizontal winds and is the thermospheric neutral velocity that the magnetosphere sees (see Smith & Aylward, 2008, for details on how this is calculated). The full details on how these modules are coupled together can be found in Smith and Aylward (2009), Yates et al (2012Yates et al ( , 2014, and Ray et al (2015). These two angular velocities combined with the height-integrated Pedersen conductance from the ionosphere module enable us to self-consistently determine the MI coupling currents and the resultant heating of the atmosphere due to the magnetospheric interaction.…”

“…Works by Yates et al (2012Yates et al ( , 2014 have shown that using a fixed Pedersen conductance, instead of a variable one, in this region does not significantly alter the local thermospheric dynamics and heating if we consider perfect coupling between the ionosphere and magnetosphere, that is, there are no field-aligned potential (FAP) drops. Work by Ray et al (2015) was the first to include FAPs in a MIT coupling model and found that neutral temperatures and flows were changed by a few percent when compared to the same MIT model without FAPs. The ionosphere and precipitating particles in this region are only recently being investigated by Jupiter's polar orbiting Juno spacecraft which will undoubtedly shed light on the conditions in this relatively unexplored region of Jupiter's upper atmosphere and high-latitude magnetosphere.…”

“…The differences in the ionospheric components of these models result in different values of Pedersen conductances, which is important in MIT coupling (e.g., Ray et al, 2015). These models do not self-consistently couple the upper atmosphere to the magnetosphere but 10.1029/2019JA026792 instead impose electric and magnetic fields, and MI coupling parameterizations onto the atmospheric model.…”

“…This coupled system is investigated using numerical models, where the neutral atmosphere is represented by a general circulation model (GCM), which is coupled to either a simplified model representing the currents Journal of Geophysical Research: Space Physics 10.1029 in the magnetosphere-ionosphere (MI) system (Ray et al, 2015;Smith & Aylward, 2009;Tao et al, 2009Tao et al, , 2010Tao et al, , 2014Yates et al, 2012Yates et al, , 2014Yates et al, , 2018 or by imposing electric fields directly into the thermospheric GCM (Achilleos et al, 1998(Achilleos et al, , 2001Bougher et al, 2005;Majeed et al, 2005Majeed et al, , 2009Majeed et al, , 2016Millward et al, 2002Millward et al, , 2005. This coupled system is investigated using numerical models, where the neutral atmosphere is represented by a general circulation model (GCM), which is coupled to either a simplified model representing the currents Journal of Geophysical Research: Space Physics 10.1029 in the magnetosphere-ionosphere (MI) system (Ray et al, 2015;Smith & Aylward, 2009;Tao et al, 2009Tao et al, , 2010Tao et al, , 2014Yates et al, 2012Yates et al, , 2014Yates et al, , 2018 or by imposing electric fields directly into the thermospheric GCM (Achilleos et al, 1998(Achilleos et al, , 2001Bougher et al, 2005;Majeed et al, 2005Majeed et al, , 2009Majeed et al, , 2016Millward et al, 2002Millward et al, , 2005.…”

“…The Smith and Aylward (2009), Tao et al (2009), Ray et al (2015, and Yates et al (2014) models all consist of a one-dimensional (1-D) magnetosphere model self-consistently coupled to a two-dimensional (2-D) atmospheric GCM. Self-consistently coupling the magnetosphere and ionosphere-thermosphere allows the field-aligned currents (FACs) to affect the magnetospheric convection electric field and magnetospheric plasma.…”