The Iogenic SO Source During the Galileo Flyby of Io
M. L. Marconi, W. H. Smyth (Atmospheric and Environmental Research)
Galileo in its December 7, 1995 encounter with Io flew through the magnetospheric wake caused by the satellite, with a closest approach altitude of 900 km. Magnetospheric instruments were able to sample the Iogenic plasma source in Io's vicinty where the plasma pickup rate should be strongly concentrated. Here we present results for the SO density along the spacecraft trajectory calculated with the AER neutral cloud model which utilizes a realistic flux distribution for the Iogenic neutral source, a Voyager based torus plasma description, and takes into account the temporal variation of the torus plasma over the period of interest. The resulting SO density is compared with a lower bound to the SO inferred by Huddlestone et al. (1997) who interpreted 2 to 3 sec magnetic field fluctuations as ion cyclotron waves generated by freshly produced SO ions and related the amplitude of these waves to the density of SO . We provide estimates of SO source rates at Io's exobase and SO source rates in the magnetosphere
Huddlestone, D. E., R. J. Strangeway, J. Warnecke, C. T. Russell,
and M. G. Kivelson, Ion Cyclotron Waves Observed at Gailieo's
Io Encounter. Warm Plasma Dispersion Analysis. Geophys. Res. Letts.,
in press, 1997.