Source During the Galileo Flyby of Io
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.