Speaker
Description
Ganymede is one of Galilean moon whose orbit is inside Jupiter's magnetosphere. The interaction between Ganymede's magnetosphere and magnetospheric plasma around the moon. This interaction results in currents carried along the magnetic flux tube to Jupiter’s ionosphere, and a bright spot called Ganymede's footprint (GFP). This work presents the location shifts of GFP in two parts. In the first part, we compared overall data of GFP location which are taken in 2007 and 2016 by Hubble Space Telescope (HST) in comparison with the average path by Bonfond et al., 2017, and the predicted locations from the 4 internal field models: GAM, VIPAL, JRM09, and JRM33. The footprints from observations show the clear discrepancies at system III longitude about 140$^\circ$ - 150$^\circ$ (the kink region) for both our data and Bonfond et al.'s average path in comparison with the predicted locations from VIPAL, JRM09, and JRM33. Nevertheless, the locations of GFP tend to be consistent with the GAM model at system III longitudes about 145$^\circ$ - 150$^\circ$ for the data observed in 2007. In the second part, we present the variation of GFP location in comparison with the evidence of volcanic eruptions on Io (internal factor) and the solar wind compression (external factor). We selected 4 specific cases which have similar CML and system III longitude to assess the effects of internal and external factors. In addition, we compared GFP locations with the field line mapping from the magnetodisc model (Nichols et al.,2015). The model results show the effects of two parameters which are the hot plasma parameter ($K_h$) and mass outflow rate from Io ($\dot{M}$). This study also considers the different cases of solar wind compression resulting in different boundary of the magnetosphere, which is chosen to be 80 R$_J$ and 50 R$_J$. The polar projection for the 4 cases reveals the shifts in the poleward or equatorward direction of GFP. Furthermore, the polar projection also shows that the main emission moves toward the poles under the solar wind compression.
