Dynamics and thermal structure of Jupiter’s thermosphere in response to magnetosphere-atmosphere coupling

Jupiter’s upper atmosphere (thermosphere/ionosphere) forms the link between its deeper atmosphere and the vast magnetosphere with its current systems, some of which close in the planet’s auroral region. The combination of acceleration and heating have profound influence on the dynamics and temperatures of Jupiter’s upper atmosphere. The ongoing Juno and future JUICE missions as well as Earth based observations provide us with new measurements and questions about the upper atmosphere structure and dynamics. Fundamentally, the aim is to understand this highly coupled upper atmosphere region which is driven to varying degrees by the magnetosphere and by the deeper atmosphere via vertically propagating waves.

Exploring such a complex system requires global numerical models. Based on our Saturn Thermosphere Ionosphere Model (STIM) [1, 2, 3], we have developed a Jupiter Thermosphere Ionosphere Model (JTIM) which includes similar features as STIM, a thermosphere model coupled chemically and dynamically to an ionosphere model. The code numerically solves the coupled non-linear Navier Stokes equations of momentum, energy and continuity, including eddy and molecular diffusion of neutral gases and full two-way ion-neutral coupling. The magnetosphere interaction is currently accounted for by mapping a magnetospheric electric field and precipitation pattern into the polar regions and allowing for particle impact ionization in the auroral regions. The thermosphere’s lower boundary is flexible to allow for coupling to the deeper atmosphere via mean background parameters and atmospheric waves.

We present first simulations of the model with a focus on the complex thermosphere dynamics and thermal structure. The use of similar models for both Saturn and Jupiter allows for direct comparisons between the planets and difference in underlying physical processes under differing boundary conditions. We also address the question of the well-known upper atmosphere temperature conundrum which is common to all giant planets in our solar system.

 

References:

[1] Müller-Wodarg et al. A global circulation model of Saturn’s thermosphere. Icarus, 180, 2006.

[2] Müller-Wodarg et al. Magnetosphere-atmosphere coupling at Saturn: 1 – Response of thermosphere and ionosphere to steady state polar forcing. Icarus, 221, 2012.

[3] Müller-Wodarg et al. Atmospheric Waves and Their Possible Effect on the Thermal Structure of Saturn's Thermosphere. Geophysical Research Letters, 46, 2019.