Cutoff Rigidities, Galactic Cosmic Ray Flux, and Heavy Ion Detections at Jupiter

A map of vertical cutoff rigidities has been calculated for galactic cosmic ray (GCR) entry into the atmosphere of Jupiter at the 1 bar pressure radius (1 RJ = 71,492 km) using the JRM33 comprehensive model of Jupiter's magnetic field (based on 32 close flybys of Jupiter by the Juno satellite) along with a particle trajectory code (Geomagnetic Cutoff Rigidity Computer Program). The map was combined with measurements of the GCR proton flux at Earth, from the BESS-Polar ii campaign, to calculate a corresponding proton flux map at Jupiter. Additional cutoff rigidity maps were calculated for 1,000 km above the 1 bar level, and for 1.41 RJ. Furthermore, detections of heavy particles from Juno's Stellar Reference Unit were analyzed for their cutoff rigidities in multiple directions. Cutoff rigidities of 3.5-7.5 GV were found for five of the detections furthest out making them possible GCR candidates. The majority of points, located below 1.6 RJ are not likely to be GCR. Assuming instead that they are trapped particles we have calculated upper and lower limits on their equatorial pitch angles, resulting in a range from 10.1 degrees to 27.1 degrees, which can help constraining Jupiter's energetic radiation. Using data of Jupiter's magnetic field, collected by the Juno satellite, we have calculated how galactic cosmic rays (energetic particles originating from supernovae) can enter into the atmosphere of Jupiter at different altitudes. This can aid our understanding of atmospheric phenomena on Jupiter and help in planning future missions to the planet. One of Juno's instruments, the Stellar Reference Unit, has detected some peculiar signatures. Some of them probably are galactic cosmic rays that have hit the instrument. Most of them are probably not, but instead they could be particles trapped by the strong magnetic field of Jupiter. If so, they can help us understand the radiation belts of the planet. Using knowledge of the location of the detections as well as the magnetic field we calculate the so-called pitch angle of the detected particles. This angle is defined by the ratio between the motion of the particle perpendicular to the magnet field line and the motion parallel to the field line. The pitch angle is fundamental in constraining energetic radiation emanating from Jupiter's atmosphere. A galactic cosmic ray cutoff rigidity map for Jupiter was made using the JRM33 model and the Geomagnetic Cutoff Rigidity Computer Program The flux of galactic cosmic ray protons into Jupiter's atmosphere was calculated based on BESS-Polar ii data Detections of heavy ions by Juno's SRU were investigated and used to estimate their equatorial pitch angles