Plasma sheet dynamics in the Jovian magnetotail: Signatures for substorm-like processes ?

During Galileo's orbit G2 in 1996 the Energetic Particles Detector (EPD) on board the spacecraft detected a number of particle bursts with large radial /antisunward anisotropies in the distant Jovian magnetotail [Krupp et al., 1998]. In this letter we focus on a detailed analysis of one of the bursts. Prior to the onset of the burst, particle intensities at low energies incr ease over several hours. This phase can be interpreted as a plasma loading phase. It ends after the onset of strong distortions in the magnetic field with a bipolar excursion of the north-south component being the most promin ent feature. The subsequent plasma sheet encounters show that the plasma sh eet has thinned considerably. Accelerated/heated ion beams first from the J ovian direction and then later from the tail direction are seen at the plas ma sheet and lobe interfaces and intense radio and plasma wave emissions ar e detected. The event is tentatively interpreted as a dynamical process, wh ere the Jovian magnetotail is internally driven unstable by mass loading of magnetic flux tubes.