Global response of the upper thermospheric winds to large ion drifts in the Jovian ovals

Abstract

AbstractWe use our fully coupled 3‐D Jupiter Thermosphere General Circulation Model (JTGCM) to quantify processes which are responsible for generating neutral winds in Jupiter's oval thermosphere from 20 µbar to 10−4 nbar self‐consistently with the thermal structure and composition. The heat sources in the JTGCM that drive the global circulation of neutral flow are substantial Joule heating produced in the Jovian ovals by imposing high‐speed anticorotational ion drifts (~3.5 km s−1) and charged particle heating from auroral processes responsible for bright oval emissions. We find that the zonal flow of neutral winds in the auroral ovals of both hemispheres is primarily driven by competition between accelerations resulting from Coriolis forcing and ion drag processes near the ionospheric peak. However, above the ionospheric peak (<0.01 µbar), the acceleration of neutral flow due to pressure gradients is found to be the most effective parameter impacting zonal winds, competing mainly with acceleration due to advection with minor contributions from curvature and Coriolis forces in the southern oval, while in the northern oval it competes alone with considerable Coriolis forcing. The meridional flow of neutral winds in both ovals in the JTGCM is determined by competition between meridional accelerations due to Coriolis forcing and pressure gradients. We find that meridional flow in the lower thermosphere, near the peak of the auroral ionosphere, is poleward, with peak wind speeds of ~0.6 km s−1 and ~0.1 km s−1 in the southern and northern oval, respectively. The corresponding subsiding flow of neutral motion is ~5 m s−1 in the southern oval, while this flow is rising in the northern oval with reduced speed of ~2 m s−1. We also find that the strength of meridional flow in both auroral ovals is gradually weakened and turned equatorward near 0.08 µbar with wind speeds up to ~250 m s−1 (southern oval) and ~75 m s−1 (northern oval). The corresponding neutral motion in this region is upward, with wind speeds up to 4 m s−1 in both ovals.