Particle bursts in the Jovian magnetosphere: Evidence for a near-Jupiter neutral line

[1] In the magnetosphere of Jupiter the plasma convection is driven by the planetary rotation up to considerable distances from the planet. However, at larger distances the rotational flow is often disrupted by explosive events, seen as jets of energetic particles propagating in the radial direction. These events are observed very frequently and can be regarded as an intrinsic property of the Jovian system. A statistical survey shows that the burst events are concentrated in the post-midnight tail region. Inward directed bursts dominate closer to the planet, outward directed bursts further away from the planet. The transition from mainly inward to mainly outward directed bursts defines the most probable location of a near-Jupiter neutral line. The findings corroborate early models which postulate that magnetic flux tubes heavily loaded with plasma originating from the moon Io will be stretched by the centrifugal forces up to such a degree that spontaneous reconnection sets in. This leads to acceleration of plasma and the release of plasmoids into interplanetary space. The process may also drive the recently observed auroral dawn storms at Jupiter.