Abstract
AbstractWe evaluate the expected effects of magnetosphere‐ionosphere coupling at Jupiter along the Juno Perijove 1 (PJ1) trajectory using an axisymmetric physical model. As found at Saturn, the model predicts distributed downward field‐aligned currents over polar regions mapping to the tail and outer magnetosphere, closed principally through a ring of upward current mapping to the middle magnetosphere, which requires downward acceleration of magnetospheric electrons generating Jupiter's main auroral emission. Auroral location, width, intensity, electron energy, and current density are in accord with values derived from previous ultraviolet imaging, such that the model forms an appropriate baseline for comparison with Juno data. We evaluate the azimuthal field perturbations during six anticipated near‐planet encounters with middle magnetosphere field lines at radial distances between ~1.6 and ~16 Jovian radii, discuss the expected form of the accelerated electron distributions, and comment briefly on model expectations in relation to first results derived from Juno PJ1 data.
Highlights
A primary goal of the Juno mission is to make the first measurements of particles, fields, and auroras directly over Jupiter’s poles [Bagenal et al, 2017]
We evaluate the expected effects of magnetosphere-ionosphere coupling at Jupiter along the
We evaluate the azimuthal field perturbations during six anticipated near-planet encounters with middle magnetosphere field lines at radial distances between ~1.6 and ~16 Jovian radii, discuss the expected form of the accelerated electron distributions, and comment briefly on model expectations in relation to first results derived from Juno Perijove 1 (PJ1) data
Summary
A primary goal of the Juno mission is to make the first measurements of particles, fields, and auroras directly over Jupiter’s poles [Bagenal et al, 2017]. Related results were presented previously by these authors evaluated on Juno planning orbits, the detailed nature of the expected field effects, i.e., their timing, and their radial distance and magnitude, and whether representing partial or complete crossings of auroral field lines, depends quite sensitively on the spacecraft trajectory It depends on the figure of the orbit (i.e., the radial distance of apoapsis for a fixed periapsis), the variable inclination of the line of apsides of the near-polar orbit to the equatorial plane, and the timing of the pass relative to the planetary rotation and orientation of the planetary magnetic axis. Brief comments on Juno instrument capabilities relative to model expectations are provided in Text S2
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