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The magnetic field and magnetosphere of Ganymede
Author(s) -
Kivelson M. G.,
Khurana K. K.,
Coroniti F. V.,
Joy S.,
Russell C. T.,
Walker R. J.,
Warnecke J.,
Bennett L.,
Polanskey C.
Publication year - 1997
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/97gl02201
Subject(s) - magnetopause , magnetosphere , physics , geophysics , dipole , magnetic field , mercury's magnetic field , jupiter (rocket family) , polar , current sheet , magnetic dipole , computational physics , l shell , spacecraft , earth's magnetic field , magnetohydrodynamics , astronomy , quantum mechanics
Within Jupiter's magnetosphere, Ganymede's magnetic field creates a mini‐magnetosphere. We show that the magnetic field measured during Galileo‧s second pass by Ganymede, with closest approach at low altitude almost directly over the moon's polar cap, can be understood to a large measure in terms of the structure of a vacuum superposition model of a uniform field and a Ganymede‐centered dipole field. Departures from the simple model can be attributed principally to magnetopause currents. We show that the orientation of the observed magnetopause normal is qualitatively consistent with expectations from the vacuum superposition model. The magnetopause currents inferred from the inbound boundary crossing are closely related to expected values, and the magnetic structure of the boundary is similar to that observed at the magnetopause of Earth. We use the vacuum magnetic field model to infer the magnetic field near Ganymede's surface, and thereby predict the particle loss cones that should be present along the spacecraft trajectory. By mapping a fraction of the corotation electric field into the polar cap, we determine expected flow velocities near closest approach to Ganymede as a function of reconnection efficiency. We conclude by discussing prospects for measurements on Galileo's remaining passes by Ganymede.