Jupiter’s magnetosphere is often contrasted with the Earth’s, in that it’s
dynamics are driven by internal processes rather than the solar wind. While
this is mostly true, the solar wind also plays a key role. At our current
level of understanding, ”mostly” controlled by internal processes could mean
60% or 90%. This is due to the near-complete lack of simultaneous,
long-baseline measurements of the solar wind and the planet’s magnetosphere.
Current and past spacecraft have focused on a diverse range of objectives, but
solar wind observations must be made outside the planet’s bow shock (at least
20 million kilometers sunward of the planet). Remote observations of the
magnetosphere and the aurora, using Earth-based telescopes, have been made but
never on a consistent and regular basis (excepting those of the Hisaki
spacecraft and ground based radio telescopes, all at very limited spatial
resolution).

We describe a concept for a small spacecraft mission to determine the relation
between solar wind conditions and the dynamics of Jupiter’s magnetosphere. The
ESPA Grande-class spacecraft, would be launched to a near-Earth (C3=0) orbit
and proceed using electric propulsion. It would preform a distant flyby of
Jupiter, spending roughly six months with 0.25 AU of the planet. In this time
it would provide continuous measurements of the solar wind magnetic field, ion
density and speed, at 10 minute resolution, and obtain well-resolved images of
Jupiter’s UV aurora and UV spectra of the Io plasma torus at roughly one hour
cadence.