Ganymede MHD Model: Magnetospheric Context for Juno's PJ34 Flyby

TL;DR

This study applies a 3D MHD model to interpret Juno's 2021 Ganymede flyby data, revealing magnetic topology and plasma distribution, and matching auroral observations with model boundaries.

Contribution

It introduces a detailed magnetospheric model analysis of Juno's Ganymede flyby, linking in situ data with global magnetic field topology and plasma conditions.

Findings

Juno did not enter the closed field line region.

The boundary between open and closed field lines matches auroral oval edges.

Model sensitivity analysis shows dependence on upstream plasma conditions.

Abstract

On June 7th, 2021 the Juno spacecraft visited Ganymede and provided the first in situ observations since Galileo's last flyby in 2000. The measurements obtained along a one-dimensional trajectory can be brought into global context with the help of three-dimensional magnetospheric models. Here we apply the magnetohydrodynamic model of Duling et al. (2014) to conditions during the Juno flyby. In addition to the global distribution of plasma variables we provide mapping of Juno's position along magnetic field lines, Juno's distance from closed field lines and detailed information about the magnetic field's topology. We find that Juno did not enter the closed field line region and that the boundary between open and closed field lines on the surface matches the poleward edges of the observed auroral ovals. To estimate the sensitivity of the model results, we carry out a parameter study with different upstream plasma conditions and other model parameters.