Date and Time: 

Friday, March 29, 2024, at 3 PM

Location: 

Ford ES&T 1229. 

Title: 

Modeling Ganymede's Interaction with the Jovian Magnetosphere: Ionospheric Outflow and the Juno PJ34 Flyby

Abstract: 

Using a hybrid model (kinetic ions, fluid electrons), we provide a three-dimensional model of Ganymede’s interaction with the Jovian magnetosphere and the moon’s ionospheric outflow. We also provide context for plasma and magnetic field observations from Juno's PJ34 flyby of Ganymede on 07 June 2021. Using five model configurations that successively increase the complexity of Ganymede’s atmosphere and ionosphere through the inclusion of additional particle species and ionization mechanisms, we examine the density and flow patterns of pick-up ions with small (H2+), intermediate (H2O+), and large (O2+) masses in Ganymede’s interaction region. The results are validated by comparing the modeled magnetic field and ion densities against time series from Juno’s magnetometer and plasma instruments. The major findings are: (a) Ganymede’s internal dipole dominated the magnetic field signature observed inside the moon’s magnetosphere, while plasma currents shaped the field perturbations within the “wake” region detected along the Jupiter-averted magnetopause. (b) Ganymede’s pick-up tail leaves a subtle, but clearly discernible imprint in the magnetic field downstream of the moon. (c) Heavy pick-up ions dominate ionospheric outflow and form a tail with steep outer boundaries. (d) During the Juno flyby, the position of Ganymede’s Jupiter-facing magnetopause varied in time due to Kelvin-Helmholtz waves traveling along the boundary layer. As such, the location of the Jupiter-facing magnetopause observed by Juno represents only a single snapshot of this time-dependent process. (e) Ionospheric hydrogen ions are partially generated outside of Ganymede’s magnetopause, forming a dilute H2+ corona that surrounds the moon’s magnetosphere. (f) Most H2O+ ions are produced at low latitudes where field lines are closed, resulting in a very dilute pick-up tail for this species.

Committee: 

Dr. Sven Simon1,2 (advisor), Dr. David Ballantyne1, Dr. A. Nepomuk Otte1, Dr. James Wray2, Dr. Lucas Liuzzo3

1     School of Physics, Georgia Institute of Technology

2     School of Earth and Atmospheric Sciences, Georgia Institute of Technology

2     Space Sciences Laboratory, University of California, Berkely