Planetary Science Seminar spring-2016

Energetic Electrons at Ceres: Implications for a Bow Shock

During Survey Orbit, Dawn’s Gamma Ray and Neutron Detector (GRaND) observed distinctive, short-lived enhancements in its exterior scintillators. Corresponding enhancements in counts in the Bismuth Germanate (BGO) scintillator were absent during this period, indicating that neither the particles responsible for the bursts in the exterior scintillators nor their progeny reached the BGO. The source of the enhancements was likely swift electrons that penetrated directly into the exterior scintillators or interacted with surrounding materials to make bremsstrahlung. If it was the latter, then the electron energies corresponding to these bursts were between 20-100 keV. These electron bursts were seen on three successive orbits over the course of a week and each time were located in the same part of the orbit in a solar wind oriented coordinate system. We postulate that these bursts were associated with the formation of a temporary bow shock associated with either a transient atmosphere or an electrically conducting Ceres interior.