The interaction of Io with the jovian magnetosphere

Abstract

The mechanical coupling of the Io torus to the jovian ionosphere and magnetosphere is discussed with particular attention to the excitation of hydromagnetic waves. It is argued that although Io will excite a highly localised disturbance in its immediate vicinity the effective trapping of hydromagnetic wave energy will lead to a substantial wake and furthermore the hydromagnetic disturbances will spread across the radial extent of the torus. It is proposed that the low frequency hydromagnetic signals detected in the torus by Pioneer and Voyager spacecraft are generated by the Io torus interaction. We conclude with a discussion of the observations of torus waves and compare position adopted here with the view that the torus magnetohydrodynamic spectrum is excited by a source external to the torus.