Investigation of Mass‐/Charge‐Dependent Escape of Energetic Ions Across the Magnetopauses of Earth and Jupiter

Abstract

We present a continuing investigation of mass‐/charge‐dependent interactions between energetic ions (greater than tens of kiloelectron volts) and planetary magnetopauses and of the escape of the ions across the boundary. Previous studies at Earth using Magnetospheric Multiscale mission data are refined and advanced showing profound behavior differences between light (H, He) and singly charged heavy ions (O+). We highlight a distinctive feature of oxygen ions: an angular distribution bifurcation providing clear indication of entrainment along the magnetopause in Speiser‐like orbits during relatively stable magnetic conditions. This signature, interpreted using a simple kinetic model, suggests that these ions tend to be carried substantial distances along the boundary (even with boundary‐normal magnetic fields) in a fashion that impedes their full dayside escape. While large fluctuations and waves can likely sometimes disrupt the observed ordering, the following picture emerges. Energetic particles with gyroradii much smaller than the magnetopause thickness (e.g., electrons and absent boundary‐normal magnetic fields) and ions with gyroradii much larger than the thickness (e.g., O+) are impeded from fully escaping across the boundary. However, energetic ions with intermediate‐sized gyroradii commensurate with the thickness (e.g., H+, He++, and O6+) can be effectively scattered within the boundary causing them to escape much more readily, with and without boundary‐normal fields. This picture is supported by observations from the Juno spacecraft at the near‐dawn meridian side of Jupiter's magnetopause. There it is observed that energetic electrons and heavy ions are more strongly contained by the magnetopause than are the energetic protons and helium ions.

Jovian Injections Observed at High Latitude

“…The problem may be similar to the problem of energetic particle escape across a magnetopause. There it is known that the gyro‐radii have profound effects (Mauk et al, ). Depending on the size of the gyro‐radii, particles may spend a substantial amount of time being transported along the boundary (in the radial direction in the case of injections).…”

Energetic Oxygen and Sulfur Charge States in the Outer Jovian Magnetosphere: Insights From the Cassini Jupiter Flyby

“…Both oxygen and sulfur ions are detected within the magnetosphere (Figure A). While oxygen and sulfur were detected in the magnetosheath, these abundances are far lower and may be a result of magnetospheric ions escaping into the magnetosheath (see Krimigis et al, ; Krupp et al, , ; Mauk et al, ). Solar wind‐originating populations (i.e., He 2+ ) are observed within the magnetospheric interval, which have been previously detected in planetary magnetospheres (e.g., Allen, Livi, & Goldstein, ; Allen, Livi, Vines, et al, ; Allen et al, , ; Ipavich & Scholer, ).…”

Heavy Ion Charge States in Jupiter's Polar Magnetosphere Inferred From Auroral Megavolt Electric Potentials

“…One such measurement is the charge state distribution of the heavy ions. Charge states can provide physical insight into the following processes: ion‐neutral interactions in Jupiter's neutral cloud (e.g., Clark et al, 2016; Kollmann et al, 2016; Lagg et al, 2003; Mauk et al, 2004; Nénon & André, 2019; Paranicas et al, 2009), ion escape across the magnetopause (Mauk et al, 2019) and solar wind entry (e.g., Allen et al, 2018, 2019), physical ion‐chemistry taking place in the vicinity of Io and Europa (e.g., Bagenal & Delamere, 2011; Delamere et al, 2007; Smith et al, 2019), acceleration mechanisms (e.g., Kronberg et al, 2019), and sources of X‐ray emissions in Jupiter's polar auroral regions (e.g., Branduardi‐Raymont et al, 2007; Cravens et al, 2003; Dunn et al, 2017; Houston et al, 2018; Jackman et al, 2018; Ozak et al, 2010).…”