Modeling Jupiter's Dawnside Magnetodisc: Using Juno Observations to Constrain a Radial Force‐Balance Model

This study investigates Jupiter's dawnside magnetodisc, using plasma and magnetic field measurements from Juno orbits 5 to 12 to refine a radial force‐balance magnetodisc model. This iterative vector potential model examines variations in the azimuthal magnetodisc current, coupled with a magnetosphere‐ionosphere coupling model from which the radial current is simultaneously obtained. Three key force‐balance parameters are used: the hot plasma parameter (pV, Pa m T−1), the mass outflow rate of cold iogenic plasma, and the height‐integrated ionospheric Pedersen conductivity. Axisymmetric equilibrium outputs are compared to Juno's residual magnetic field and heavy ion density data between 15 and 60 RJ. Optimal parameter values for each orbit and overall current distributions are determined. Averaged modeled values are (1.63 ± 0.17) × 107 Pa m T−1 for the hot plasma parameter, 1,340 ± 350 kg s−1 for the mass outflow rate, and 0.26 ± 0.08 mho for the Pedersen conductivity. The overall modeled magnetodisc azimuthal current to 60 RJ is 266 ± 23 MA, varying similarly to the currents determined by Connerney et al. (2020, https://doi.org/10.1029/2020JA028138) but typically ∼50 MA larger. Of this total, the hot plasma current 158 ± 13 MA is larger than the cold plasma current 109 ± 23 MA, and dominates in the inner region. The cold plasma current typically becomes the larger component beyond ∼35 RJ and exhibits greater orbit‐to‐orbit variability. The mass outflow rate from Io is the primary driver of magnetodisc current variability. The north‐south summed radial magnetosphere‐ionosphere coupling current 104 ± 31 MA is typically ∼40% of the total azimuthal current, with variations that are only weakly correlated.