Bucking the Current: Connecting Mass Loss Down Jupiter's Magnetotail to the Dawn-Dusk Electric Field at the Io Plasma Torus
Thursday, 26 May 2016
Jeffrey P Morgenthaler, Planetary Science Institute Fort Kent, Fort Kent, ME, United States, Fabiola Pinho Magalhaes, INPE, Sao Jose dos Campos, Brazil, Max Marconi, Prisma Basic Research, Niagara Falls, NY, United States and Ronald J Oliversen, NASA Goddard Space Flight Center, Greenbelt, MD, United States
Abstract:
Observations of the Io plasma torus (IPT) reveal a systematic shift of the IPT toward the dawn. Barbosa & Kivelson (1983) showed that this shift is caused by a dawn-to-dusk electric field which is induced by ExB drift when material moves down the magnetotail. The electric field propagates to the region of the IPT by slightly opposing the current in the current current sheet and thus perturbing the magnetic field in the lobes. Precise calculations have yet to be done which would enable a quantitative relationship between the torus shift, measurable with telescopes as small as 28 cm (Nozawa et al. 2004), and the amount of material flowing down the Jovian magnetotail. Renewed motivation for these calculations is provided by the work of Louarn et al. (2014), who suggest that the departure of material down the magnetotail may drive the release of material from the IPT. We have an extensive set of ground-based coronagraphic observations of the IPT (1997 -- 2008), which provide both IPT brightness and shift as a function of time. An even larger set (1990 -- 2008) of spectroscopic observations of Io in the forbidden oxygen red line provide information on the evolution of density enhancements in the IPT, also a component of the Louarn et al. picture. By quantitatively connecting the amount of material leaving the magnetotail, the response of the total torus brightness, and the evolution of individual IPT density enhancements, we can test the Louarn et al. (2014) hypothesis of what drives radial departure of material from the IPT. The missing piece is a quantitative relationship between the IPT shift and the amount of material leaving the magnetotail. This work could also help determine the amount of material leaving the magnetosphere through the small-scale "drizzle" on the flanks of the magnetosphere, which Bagenal (2007) suggests may make up the bulk of the mass loss to the solar wind and provides motivation for continued synoptic monitoring of the plasma torus and Io volcanic activity.
