Periodic plasma escape from the mass‐loaded Kronian magnetosphere

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94967/1/jgra20364.pd

Outer magnetospheric structure: Jupiter and Saturn compared

The Jovian dayside magnetosphere is traditionally divided into three different regions with the outermost region, colloquially referred to as the cushion region, existing between the outer edge of the magnetodisk and the magnetopause. Magnetometer and plasma data from 6 different spacecraft are used to determine the average properties of this region, including its characteristic thickness at the subsolar point, and these observations are compared with data from the Saturnian magnetosphere obtained using the Pioneer, Voyager, and Cassini spacecraft. Significant differences are found in the structure of the two rotationally driven magnetospheres with the Saturnian system showing little evidence for the cushion region seen at Jupiter. These differences are discussed in terms of the parameter regimes pertinent to each planet, and the potential effect of magnetodisk warping at Saturn is discussed. It is tentatively suggested that while the Jovian magnetodisk typically breaks down several tens of planetary radii inside the magnetopause, thus allowing plasma-depleted flux tubes beyond it to relax into the cushion region configuration, the Saturnian magnetodisk may persist until much closer to the magnetospheric boundary. A number of observational tests of this hypothesis are proposed, and the need for improved observations at both planets is stressed

A possible auroral signature of a magnetotail reconnection process on Jupiter

[1] Several theoretical models and in situ observations consistently suggest that the process of nightside reconnection associated with Earth's magnetospheric substorms is also taking place in the midnight tail region of Jupiter. We report the observation of a new auroral feature which takes the form of isolated spots appearing near the northern dusk-midnight limb, poleward of the main auroral oval. This feature was clearly detected in three HST-STIS data sets obtained on 14, 16, and 18 December 2000. Its position poleward of the main auroral oval, and lagging corotation, shows that it is magnetically connected to a distant region of the nightside magnetosphere. It is therefore suggested that these transient spots are the auroral signatures of reconnection processes occurring in the nightside tail of the distant Jovian magnetosphere. The cause of this reconnection is somewhat analogous to the case of a solar coronal mass ejection, so one may refer to it as a "Jovian mass ejection.'

Joule heating associated with auroral electrojets during magnetospheric substorms

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95557/1/jgra20835.pd