Time-varying magnetospheric environment near Enceladus as seen by the Cassini magnetometer

Abstract

In 2008, the Cassini spacecraft made four close Enceladus flybys along similar trajectories. During these flybys the magnetometer recorded the time-varying magnetic field associated with the plasma interaction with Enceladus and its plume. Close to Enceladus, the Cassini magnetometer observed 4% to 7% enhancement in the magnetic field magnitude, associated with the slowing down of the ambient plasma. Herein we examine these four flybys, estimate the deceleration of the flow, locate the momentum-loading center for each pass, and compare their pass to pass variability. Even though the spacecraft trajectories were similar, two different types of perturbations were observed at distances greater than 5 Enceladus radii downstream, and to the north of the moon. Ion-cyclotron waves were observed during each of the flybys, with pass to pass wave amplitudes varying in a similar manner as the enhancement of the field magnitude.