Jupiters high energy particle environment observed by Juno

The Advanced Stellar Compass (ASC), part of the MAG experiment onboard Juno, has been measuring the Jovian high energy particle environment since orbit insertion. We’ve produced a detailed map of the distribution of trapped high energy particles, predominantly electrons (>10MeV), using data from Juno’s first 47 orbits. The observations also demonstrate the significant influence that space weather at Jupiter has on the local particle flux. The ASC is a star tracker designed with four low light cameras to provide accurate attitudes for the MAG experiment’s vector magnetometers, located on a boom at the end of one of the spacecraft solar wings at 10 and 12m from the center of the spacecraft. At this location the ASC cameras are subjected to the high energy particle omniflux for all 4pi.  Electrons with an average energy of 20MeV and protons with energy in excess of 100MeV will pass through the camera radiation shielding to the camera CCDs to liberate signal electrons. To enable robust attitude estimation, the signal from the penetrating radiation is first removed by a software filter before star field recognition is performed. Registering the particle count in each image, these measurements effectively provide for a high time resolution measurement of the high energy particle omniflux. We present the detailed map of high energy particles throughout Jupiter’s magnetosphere and demonstrate how the local flux responds to solar activity.