Plasma sheet dynamics in the Jovian magnetotail: Signatures For substorm‐like processes ?

During Galileo's orbit G2 in 1996 the Energetic Particles Detector (EPD) onboard 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 increase 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 prominent feature. The subsequent plasma sheet encounters show that the plasma sheet has thinned considerably. Accelerated/heated ion beams first from the Jovian direction and then later from the tail direction are seen at the plasma sheet and lobe interfaces and intense radio and plasma wave emissions are detected. The event is tentatively interpreted as a dynamical process, where the Jovian magnetotail is internally driven unstable by mass loading of magnetic flux tubes.