Modeling Ganymede's Interactions with the Jovian  Magnetosphere

About this research:

3-D Multi-fluid simulations are used to examine the magnetosphere and ionosphere of Ganymede and how they couple to the Jovian magnetospheric system.  Ganymede is an icy moon of Jupiter that orbits at 15.1 Jupiter radii and possesses its own ionosphere and magnetosphere.  This orbit location places Ganymede within the corotaional plasmasphere of Jupiter where it is shielded from the solar wind but subjected to Jupiter's rapidly corotating and periodically wobbling magnetosphere.  The multitude of data retrieved from the Galileo satellite on this system combined with results from Hubble Space Telescope have brought to light many questions as to the general energization of plasma near Ganymede and the importance of coupling between the magnetospheres and ionospheres of Jupiter and Ganymede.  Energization of plasma expressed as aurora have been observed both at the magnetic footprint of Ganymede on Jupiter's ionosphere [Clarke et al., 1998] and at Ganymede [Feldman et al., 2000]. Current endeavors to model and understand the Jovian magnetosphere along with data from the Galileo spacecraft help to constrain Ganymede's near space environment, making it possible to create a realistic model.  A sub-Alfvénic, super sonic flow of incident magnetized plasma shapes Ganymede's magnetosphere, an interaction believed to be unique in the solar system as Ganymede is the only Galilean moon with an intrinsic magnetic field and magnetosphere.

Ganymede's magnetosphere is supported through two major plasma sources; the incident Jovian plasma and Ganymede's own ionosphere.  The multi-fluid simulations enable us to track these sources in order to determine their effects on the system, specifically, which species govern reconnection processes in Ganymede's magnetotail, and which are significantly heated and allowed to precipitate. The precipitation of plasma into Ganymede's diffuse atmosphere and below produce both the observed auroral emissions and sputter the icy surface to generate the atmosphere and ionosphere. Multi-fluid simulations are particularly useful for studying complicated coupled systems like that of Ganymede and Jupiter's where several high mass ion species dominate the energy and momentum transport.  In understanding the contributions of all the plasma sources to the system and the external currents they generate, we also take one step closer to understanding the implications from the magnetometer data of a conductive subsurface ocean [Kivelson et al., 2002]. Images can be enlarged by clicking on them.     



 Flyby magnetometer comparison
Comparison of the magnetometer data
from the G28 flyby of the Galileo
spacecraft (black) to a static
superposition (green) and the multi-fluid
simulation (blue).
Comparison with Feldman et al., 2000 
A comparison of the trailing side
temperatures of the three ion species.
JMP is Jovian magnetospheric plasma
and H+ and O+ are from Ganymede's
ionosphere.
Again a view of temperatures at the
ionospheric altitude of the JMP
compared to the auroral observations
of the HST from  Feldman et al. [2000].
Notice precipitation appears enabled
through the enhanced cusps.
Pressure Comparison 
A side view of the pressures of each of
the ion species.  Notice the high pressure
of the O+.  While high densities of H+
exist in Ganymede's  inner magnetosphere,
the O+ is preferentially heated in the tail.

Who's Doing It:

Geophysics Main Page | Program Information | Solid Earth | Near-Surface | Space Physics
Modeling Ganymede's Magnetosphere / 30 November 2004 / cpaty at u.washington.edu