Mass release at Jupiter: Substorm‐like processes in the Jovian magnetotail

The Jupiter orbiting spacecraft Galileo has provided evidence that the Jovian magnetotail is subject to a periodic process with typical timescales of several days by which the Jovian system is presumably releasing its excess iogenic mass. The mass release process resembles a terrestrial substorm in the sense of a global reconfiguration of the magnetotail. During the initial “loading” phase the plasma convection is at a moderate speed in the corotation direction and the Jovian plasma sheet appears to be in a stable configuration. In the release phase, reconnection through a thinned current sheet leads to radially inward and outward plasma flows and the ejection of plasmoids. Storage of magnetic energy in the lobe region seems not to be the prime driver of the reconfiguration process. Therefore the role of the solar wind as energy source is of less importance than for terrestrial substorms. Instead, it can be envisaged that plasma loading of fast rotating magnetic flux tubes and the associated centrifugal forces drive the reconfiguration process.