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Altitude of Saturn's aurora and its implications for the characteristic energy of precipitated electrons
Bonfond, B.; Clarke, J. T.; Gérard, J. -C. +4 more
Images of Saturn's aurora at the limb have been collected with the Advanced Camera for Surveys on board the Hubble Space Telescope. They show that the peak of Saturn's nightside emission is generally located 900-1300 km above the 1-bar level. On the other hand, methane and H2 columns overlying the aurora have been determined from the an…
Equatorward diffuse auroral emissions at Jupiter: Simultaneous HST and Galileo observations
Krupp, N.; Woch, J.; Menietti, J. D. +6 more
We study the auroral emissions equatorward of the main oval based on Hubble Space Telescope (HST) observations of both Jovian hemispheres on September 20, 1997. On the same day, Galileo observed changes in the electron pitch angle distribution between the inner and middle magnetosphere (PAD boundary), indicative of electron diffusion. This region,…
Saturn's equinoctial auroras
Dougherty, M. K.; Kurth, W. S.; Mitchell, D. G. +13 more
We present the first images of Saturn's conjugate equinoctial auroras, obtained in early 2009 using the Hubble Space Telescope. We show that the radius of the northern auroral oval is ∼1.5° smaller than the southern, indicating that Saturn's polar ionospheric magnetic field, measured for the first time in the ionosphere, is ∼17% larger in the nort…
Observations of Jovian polar auroral filaments
Nichols, J. D.; Clarke, J. T.; Grodent, D. +1 more
In this paper we report a phenomenon hitherto unobserved in Jupiter's ultraviolet polar auroras, specifically thin (∼0.6° wide), long-lived quasi-sun-aligned polar auroral filaments (PAFs) of brightness ∼100 kR spanning the highly variable region poleward of the main oval. This observation, made using Hubble Space Telescope images, is significant …
Signatures of field-aligned currents in Saturn's nightside magnetosphere
Coates, A. J.; Dougherty, M. K.; Khurana, K. K. +4 more
We report first results of a survey of near-simultaneous and near-conjugate magnetic field perturbations observed over Saturn's northern and southern nightside auroral regions on ∼40 periapsis passes of the Cassini spacecraft during 2008. Structured azimuthal fields that are generally anti-symmetric north and south were observed at auroral latitud…