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Article Dans Une Revue Geophysical Research Letters Année : 2017

Intense Harmonic Emissions Observed in Saturn's Ionosphere

Résumé

The Cassini spacecraft’s first Grand Finale orbit was carried out in April 2017. This set of 22 orbits had an inclination of 63° with a periapsis grazing Saturn’s ionosphere, thus providing unprecedented coverage and proximity to the planet. Cassini’s Radio and Plasma Wave Science instrument repeatedly detected intense electrostatic waves and their harmonics near closest approach in the dayside equatorial topside ionosphere. The fundamental modes were found to both scale and trend best with the H^{+} plasma or lower hybrid frequencies, depending on the plasma composition considered. The fine-structured harmonics are unlike previous observations, which scale with cyclotron frequencies. We explore their generation mechanism and show strong evidence of their association with whistler mode waves, consistent with theory. The possibility of Cassini’s presence in the ionosphere influencing the resonance and harmonics is discussed. Given their link to the lower hybrid frequency, these emissions may offer clues to constraining Saturn’s ionospheric properties.

Dates et versions

hal-02639659 , version 1 (28-05-2020)

Identifiants

Citer

Ali H. Sulaiman, William S. Kurth, Ann M. Persoon, John D. Menietti, William M. Farrell, et al.. Intense Harmonic Emissions Observed in Saturn's Ionosphere. Geophysical Research Letters, 2017, 44 (24), pp.12,049-12,056. ⟨10.1002/2017GL076184⟩. ⟨hal-02639659⟩
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