Ganymede’s magnetic footprint mapping: Modeling and HST observations
- 1Ph.D. program in Applied Physics, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
- 2Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
- 3National Astronomical Research Institute of Thailand (Public Organization), Maerim Chiang Mai, 50180, Thailand
- 4Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
- 5Center for Space Physics, Boston University, Boston, MA, USA
In this work, the locations of observed Ganymede’s magnetic footprint were compared with the locations predicted by the magnetic field model under different plasma conditions. The shifts of Ganymede's magnetic footprint locations from average footpath given by Grodent et al. (2008) were analyzed. The average path is created from about 1000 images taken by instruments onboarded Hubble Space Telescope (HST). The position shifts indicate the variation of magnetic field line mapping from Ganymede to Jupiter’s ionosphere. The two sets of data from HST were analyzed to obtain the locations of Ganymede’s magnetic footprint in 2007 and 2016. For both sets of data, at longitude ranging approximately from 170° to 180°, we found that the locations were significantly shifted in poleward direction between 0.5° to 2° from the average footpath. Different from data in May 2007, the Ganymede’s magnetic footprint locations in May 2016 at longitude about 160° could possibly locate in equatorward direction. At orbital distance of Ganymede about 15 RJ, in Jupiter’s middle magnetosphere, there is strong influence of plasma, whose major source is Io’s volcanic eruptions. Thus, the variations of plasma resulting in the stretching of magnetic field lines affect the magnetic field mapping from Ganymede to ionosphere. Furthermore, based on the magnetodisc model, the hot plasma pressure anisotropy strongly influences the stretching of the field lines and the mapped locations of Ganymede’s footprint in ionosphere to be shifted in either poleward or equatorward directions. In this study, we detected both poleward and equatorward shifts in different observations, whose connection with the plasma environment in the middle magnetosphere awaits for further study.
How to cite: Promfu, T., Wannawichian, S., Nichols, J., and Clarke, J.: Ganymede’s magnetic footprint mapping: Modeling and HST observations, Europlanet Science Congress 2020, online, 21 Sep–9 Oct 2020, EPSC2020-105, https://doi.org/10.5194/epsc2020-105, 2020.