High-Energy (>10 MeV) Oxygen and Sulfur Ions Observed at Jupiter From Pulse Width Measurements of the JEDI Sensors.

The Jovian polar regions produce X-rays that are characteristic of very energetic oxygen and sulfur that become highly charged on precipitating into Jupiter's upper atmosphere. Juno has traversed the polar regions above where these energetic ions are expected to be precipitating revealing a complex composition and energy structure. Energetic ions are likely to drive the characteristic X-rays observed at Jupiter (Haggerty et al., 2017, https://doi.org/10.1002/2017GL072866; Houston et al., 2018, https://doi.org/10.1002/2017JA024872; Kharchenko et al., 2006, https://doi.org/10.1029/2006GL026039). Motivated by the science of X-ray generation, we describe here Juno Jupiter Energetic Particle Detector Instrument (JEDI) measurements of ions above 1 MeV and demonstrate the capability of measuring oxygen and sulfur ions with energies up to 100 MeV. We detail the process of retrieving ion fluxes from pulse width data on instruments like JEDI (called "puck's"; Clark, Cohen, et al., 2016, https://doi.org/10.1002/2017GL074366; Clark, Mauk, et al., 2016, https://doi.org/10.1002/2015JA022257; Mauk et al., 2013, https://doi.org/10.1007/s11214-013-0025-3) as well as details on retrieving very energetic particles (>20 MeV) above which the pulse width also saturates.

Pluto's Interaction With Energetic Heliospheric Ions.

Pluto energies of a few kiloelectron volts and suprathermal ions with tens of kiloelectron volts and above. We measure this population using the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument on board the New Horizons spacecraft that flew by Pluto in 2015. Even though the measured ions have gyroradii larger than the size of Pluto and the cross section of its magnetosphere, we find that the boundary of the magnetosphere is depleting the energetic ion intensities by about an order of magnitude close to Pluto. The intensity is increasing exponentially with distance to Pluto and reaches nominal levels of the interplanetary medium at about 190R P distance. Inside the wake of Pluto, we observe oscillations of the ion intensities with a periodicity of about 0.2 hr. We show that these can be quantitatively explained by the electric field of an ultralow-frequency wave and discuss possible physical drivers for such a field. We find no evidence for the presence of plutogenic ions in the considered energy range.

The "Puck" energetic charged particle detector: Design, heritage, and advancements.

Energetic charged particle detectors characterize a portion of the plasma distribution function that plays critical roles in some physical processes, from carrying the currents in planetary ring currents to weathering the surfaces of planetary objects. For several low-resource missions in the past, the need was recognized for a low-resource but highly capable, mass-species-discriminating energetic particle sensor that could also obtain angular distributions without motors or mechanical articulation. This need led to the development of a compact Energetic Particle Detector (EPD), known as the "Puck" EPD (short for hockey puck), that is capable of determining the flux, angular distribution, and composition of incident ions between an energy range of ~10 keV to several MeV. This sensor makes simultaneous angular measurements of electron fluxes from the tens of keV to about 1 MeV. The same measurements can be extended down to approximately 1 keV/nucleon, with some composition ambiguity. These sensors have a proven flight heritage record that includes missions such as MErcury Surface, Space ENvironment, GEochemistry, and Ranging and New Horizons, with multiple sensors on each of Juno, Van Allen Probes, and Magnetospheric Multiscale. In this review paper we discuss the Puck EPD design, its heritage, unexpected results from these past missions and future advancements. We also discuss high-voltage anomalies that are thought to be associated with the use of curved foils, which is a new foil manufacturing processes utilized on recent Puck EPD designs. Finally, we discuss the important role Puck EPDs can potentially play in upcoming missions.

Dynamics of Saturn's magnetosphere from MIMI during Cassini's orbital insertion.

The Magnetospheric Imaging Instrument (MIMI) onboard the Cassini spacecraft observed the saturnian magnetosphere from January 2004 until Saturn orbit insertion (SOI) on 1 July 2004. The MIMI sensors observed frequent energetic particle activity in interplanetary space for several months before SOI. When the imaging sensor was switched to its energetic neutral atom (ENA) operating mode on 20 February 2004, at approximately 10(3) times Saturn's radius RS (0.43 astronomical units), a weak but persistent signal was observed from the magnetosphere. About 10 days before SOI, the magnetosphere exhibited a day-night asymmetry that varied with an approximately 11-hour periodicity. Once Cassini entered the magnetosphere, in situ measurements showed high concentrations of H+, H2+, O+, OH+, and H2O+ and low concentrations of N+. The radial dependence of ion intensity profiles implies neutral gas densities sufficient to produce high loss rates of trapped ions from the middle and inner magnetosphere. ENA imaging has revealed a radiation belt that resides inward of the D ring and is probably the result of double charge exchange between the main radiation belt and the upper layers of Saturn's exosphere.

Energetic particles at venus: galileo results.

At Venus the Energetic Particles Detector (EPD) on the Galileo spacecraft measured the differential energy spectra and angular distributions of ions >22 kiloelectron volts (keV) and electrons > 15 keV in energy. The only time particles were observed by EPD was in a series of episodic events [0546 to 0638 universal time (UT)] near closest approach (0559:03 UT). Angular distributions were highly anisotropic, ordered by the magnetic field, and showed ions arriving from the hemisphere containing Venus and its bow shock. The spectra showed a power law form with intensities observed into the 120- to 280-keV range. Comparisons with model bow shock calculations show that these energetic ions are associated with the venusian foreshock-bow shock region. Shock-drift acceleration in the venusian bow shock seems the most likely process responsible for the observed ions.