A new perspective concerning the influence of the solar wind on the Jovianmagnetosphere

The solar wind exerts a strong influence on the Jovian magnetosphere in cha nging its volume, in energizing plasma, and in stimulating the aurora and a host of other associated effects. However, whereas at Earth the dominant s olar terrestrial coupling process is magnetic reconnection, the dominant en ergy reservoir in Jupiter's magnetospheric plasma, continually present, is the kinetic energy of its rotating plasma disk. This "flywheel"' produces e ffects with no terrestrial analogy, some of which we describe here. The mos t surprising prediction from the analysis of this paper is that remotely se nsed symptoms of Jovian magnetospheric activity are likely to occur in conj unction with solar wind pressure decreases. Compressions of the magnetosphe re produced by forward shocks and other solar wind pressure increases will heat the magnetospheric plasma but substantially reduce the ionosphere-magn etosphere current systems. The intensity of dayside aurora and of radio wav e emissions associated with increased ionospheric-magnetospheric current sy stems will tend to anticorrelate with magnetospheric compressions and corre late with expansions. The link to the aurora is based on an argument that t he auroral zone maps to the plasma disk of the middle magnetosphere and is thus linked to plasma sheet dynamics. The effect of expansion on the plasma sheet is to increase the parallel pressure, setting up conditions that can produce detached plasma "blobs" and enhance mass loss. The analysis is par ticularly apposite in light of the opportunities for observing Solar wind-J ovian interactions using data from both the Galileo and the Cassini spacecr aft during the Cassini flyby of Jupiter in late 2000, ideally supplemented by auroral imaging with ground-based and Hubble telescopes.