Loss of Energetic Ions Comprising the Ring Current Populations of Jupiter's Middle and Inner Magnetosphere

Abstract

The low‐altitude, polar orbit of the Juno mission allows the Jupiter Energetic Particle Detector Instrument to view into, and resolve, the loss cone of energetic ions comprising the low‐altitude extension of Jupiter's ring current ions. For regions mapping from just inside Ganymede's orbit to well beyond Ganymede's orbit, energetic ions (>50 keV H+ and >130 keV Oxygen and Sulfur ions) are strongly scattered into the loss cone and lost to the magnetosphere at the “strong diffusion limit” at essentially all times. We conclude, by arguing against magnetic curvature scattering, that the cause is waves, perhaps associated with Alfvénic variations previously documented in this equatorial region. Scattering is generally weak or nonexistent near the orbits of the moons Europa and Io, except for the regions just downstream of the corotating plasmas. For Io, we sometimes observe moderate, but not saturated, scattering within roughly 60° downstream. Significantly, scattering is weak or nonexistent just upstream of Io's position, an asymmetry echoed in some previous wave observations. A preliminary accounting of the total (longitude‐averaged) scattering losses near Io's orbit yields loss rates of order 4%–5% of the strong diffusion limit for H+ and 5%–7% for heavy ions (O + S). We conclude that near Io's orbit, charge exchange losses likely dominate over scattering losses for heavy ions and for the lower energy H+ ions (roughly <200 keV).

A Survey of Magnetic Field Line Curvature in Jovian Dawn Magnetodisc

“…This study reveals that FLC scattering widely influences the motions of ions and relativistic electrons in the predawn sector of Jupiter's CS, which suggests that it may be one of the primary sources of auroral ion precipitation. This is different from which in the inner and middle region of Jupiter's magnetosphere (Mauk et al, 2022), showing the differences between different regions. Jupiter's X-ray aurora can be generated by precipitating ions through acceleration near the auroral region (Cravens et al, 2003;Dunn et al, 2017;Metzger et al, 1983) and precipitating relativistic electrons through bremsstrahlung (Branduardi-Raymont et al, 2008).…”

“…As for the more energetic ions, such as 1 MeV oxygen ions, the time it takes for them to pass through this region is too short, and the large Larmor radii make the motions more complex. Wave‐particle interaction may be the main cause of their diffusion instead of FLC scattering (Mauk et al., 2022).…”

“…FLC has been widely investigated in the terrestrial magnetosphere using multi-spacecraft data (Rogers et al, 2023;Saito et al, 2011;Shen et al, 2003;Y. C. Zhang et al, 2016) and in the inner and middle regions of Jupiter's magnetosphere using data from Voyager 1 and Juno (Mauk & Krimigis, 1987;Mauk et al, 2022;Paranicas et al, 1991) and the magnetospheric model (Birmingham, 1982(Birmingham, , 1984. The observation-based investigation of FLC in the outer region of Jupiter's magnetosphere is rarely proposed so far.…”

“…The observation-based investigation of FLC in the outer region of Jupiter's magnetosphere is rarely proposed so far. The main cause of pitch angle diffusion (into the loss cone) is thought to be waves against FLC scattering in the inner and middle regions of Jupiter's magnetosphere (Mauk et al, 2022), while the main cause of it in the outer regions remain uncertain. To comprehensively understand the magnetic structure and particle behaviors in Jupiter's magnetosphere, we proposed a method based on Minimum Variation Analysis (MVA) (Lepping & Behannon, 1980;Sonnerup & Scheible, 1998) and Harris model (Harris, 1962) to obtain FLC in Jupiter's CS using data from Juno Magnetic Field investigation (MAG) (Connerney, 2022).…”

Energetic electron lensing caused by Ganymede's magnetic field

“…Uncertainties in particle trajectory calculations are small (<5% in the gyration radius), dominated by the accumulation of errors in numerical integration and the fidelity of the magnetic models used. Since particle motion is simulated 15R J away from Jupiter, the magnetic model uncertainties are minimal but for possible time variability of the magnetodisc (Caudal, 1986;Mauk et al, 1998Mauk et al, , 2022. However, uncertainties in Ganymede's magnetospheric interaction fields (Kivelson et al, 2002) and those due to the interaction with Jupiter's field will directly impact simulated particle motions, and to a lesser extent, the total lensing effect.…”