Favorable Conditions for Magnetic Reconnection at Ganymede's Upstream
Magnetopause
Abstract
Ganymede is the only Solar System moon known to generate a permanent
magnetic field. Jovian plasma motions around Ganymede create an upstream
magnetopause, where energy flows are thought to be driven by magnetic
reconnection. Simulations indicate Ganymedean reconnection events may be
transient, but the nature of magnetopause reconnection at Ganymede
remains poorly understood, requiring an assessment of reconnection onset
theory. We present an analytical model of steady-state conditions at
Ganymede’s magnetopause, from which the first Ganymedean reconnection
onset assessment is conducted. We find that reconnection may occur
wherever Ganymede’s closed magnetic field encounters Jupiter’s ambient
magnetic field, regardless of variations in magnetopause conditions.
Unrestricted reconnection onset highlights possibilities for multiple
X-lines or widespread transient reconnection at Ganymede. The
reconnection rate is controlled by the ambient Jovian field orientation
and hence driven by Jupiter’s rotation. Future progress on this topic is
highly relevant for the JUpiter ICy moon Explorer (JUICE) mission.