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Takehiko Satoh (FRCCS/Science Univ of Tokyo), J.E.P. Connerney (NASA/GSFC)
Satoh and Connerney (Icarus 141, 236, 1999) analyzed IRTF-NSFCAM images of Jupiter's H3+ aurorae and studied the longitude-dependent emission intensity by constructing an emission source model based on the VIP4 magnetic field model (Connerney et al., JGR 103, 11929, 1998). To simplify the emission source model, they introduced a mathematical expression to modulate the intensity as a function of longitude. Their model successfully reproduced the observed auroral features and revealed the longitudinal variations: (i) which are consistent with the windshield-wiper effect of drifting electrons trapped in the middle magnetosphere, and (ii) for regions connected to great distances of the magnetosphere, the emission intensity peak occurs near the longitude of minimum surface magnetic field strength, consistent with a rapid pitch angle scattering in the corresponding source region.
In this study, we construct a physical model to reproduce the observed intensity variations. The particle precipitation flux is estimated based on the Prange and Elkhamsi model (JGR 96, 21371, 1991) but with the VIP4 magnetic field model. Prange and Elkhamsi used the O4 model which significantly differs from the VIP4 model especially in the south. We have generated auroral rings by tracing the magnetic field lines from equatorial distances ranging between 6 R\rm j (Jovian radii) and 30 R\rm j. Magnetic field strengths at the equator and at the surface (both hemispheres) as well as the dip angle determine the flux of immediately precipitating particles. Particles with a pitch angle between the local loss cone and the drift cone are stored and yield the windshield-wiper effect. Although the model requires mathematically-modeled emission added in the polar cap, we have found that the precipitation flux model reproduces the observed intensity variations between 6 R\rm j and 30 R\rm j fairly well. Details of the model, as well as the effect of the pitch-angle distribution and the pitch-angle scattering will be discussed.
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