P52A-08:
Observation of High Density Plasma in the Vicinity of Europa and its Potential Relationship with Plume Activity
Friday, 19 December 2014: 12:05 PM
William R Paterson1, Edward C Sittler Jr2, John F Cooper3, Richard E Hartle2 and Alexander S Lipatov4, (1)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (2)NASA Goddard SFC, Greenbelt, MD, United States, (3)NASA Goddard Space Flight Center, Code 670, Greenbelt, MD, United States, (4)University of Maryland Baltimore County, Baltimore, MD, United States
Abstract:
During the course of the Galileo Mission at Jupiter, the spacecraft obtained high-resolution observations of plasmas during 8 near encounters with Europa. Most typically, these encounters provided evidence of modest production of plasma within Europa’s exosphere, with ion densities comparable to that of the plasma sheet. However, plasma densities significantly greater than those of the surrounding plasma sheet were seen during two encounters. Once, as the spacecraft traversed the moon’s near-downstream wake with respect to the prevailing flow of Jupiter’s plasma sheet/plasma torus. Densities were several times higher than those of the plasma sheet, and entrainment of Europa’s ionosphere accounts for this observation. The other encounter occurred in the upstream region. Densities were an order of magnitude higher than usual, and this has been interpreted as potential evidence of ionization within a water plume. However, the usual signatures of fresh ion production that would be expected in a plume are not found in the ion energy-angle spectra. The observations and possible explanations are presented in this report.
