Journal article
Ring Shadowing Effects on Saturn's Ionosphere: Implications for Ring Opacity and Plasma Transport
Geophysical research letters, Vol.45(19), pp.10084-10,092
10/16/2018
DOI: 10.1029/2018GL079150
Abstract
We present new results obtained by the Radio and Plasma Wave Science Langmuir probe on board Cassini during the Grand Finale. The total direct current sampled by the Langmuir probe at negative bias voltage is used to study the effect of the ring shadows on the structure of the Kronian topside ionosphere. The D and C rings and the Cassini Division are confirmed to be optically thin to extreme ultraviolet solar radiation. However, different responses from the opaque A and B rings are observed. The edges of the A ring shadow are shown to match the A ring boundaries, unlike the B ring, which indicates variable responses to the B ring shadow. We show that the variable responses are due to the ionospheric plasma, more precisely to the longer chemical lifetime of H+ compared to H-2(+) and H-3(+), suggesting that the plasma is transported from the sunlit region to the shadowed one in the ionosphere. Plain Language Summary As Saturn's northern hemisphere experienced summer during the Grand Finale, the planet's northern dayside hemisphere and its rings were fully illuminated by the Sun. However, the southern hemisphere was partly obscured because of the shadows cast by the A and B rings. Using the in situ measurements of the Langmuir probe part of the Radio and Plasma Wave Science investigation on board the Cassini spacecraft, we study for the first time the effect of the ring shadows on Saturn's ionosphere. From the ring shadows signatures on the total ion current collected by the Langmuir probe, we show that the A and B rings are optically thicker (to the solar extreme ultraviolet radiation) than the inner C and D rings and the Cassini Division to the solar extreme ultraviolet radiation. Moreover, we reproduce the boundaries of the A ring and the outer edge of the B ring. Furthermore, observed variations with respect to the inner edge of the B ring imply a delayed response of the ionospheric H+ because of its long lifetime and suggest that the ionospheric plasma is transported from an unshadowed region to a shadowed one in the ionosphere.
Details
- Title: Subtitle
- Ring Shadowing Effects on Saturn's Ionosphere: Implications for Ring Opacity and Plasma Transport
- Creators
- Lina Z Hadid - Swedish Institute of Space PhysicsMichiko W. Morooka - Swedish Institute of Space PhysicsJan-Erik Wahlund - Swedish Institute of Space PhysicsL. Moore - Boston UniversityT. E. Cravens - University of KansasM. M. Hedman - University of IdahoNiklas J. T. Edberg - Swedish Institute of Space PhysicsErik Vigren - Swedish Institute of Space PhysicsJ H Waite Jr - Southwest Research InstituteR. Perryman - Southwest Research InstituteW. S. Kurth - University of IowaW. M. Farrell - Goddard Space Flight CenterAnders I. Eriksson - Swedish Institute of Space Physics
- Resource Type
- Journal article
- Publication Details
- Geophysical research letters, Vol.45(19), pp.10084-10,092
- DOI
- 10.1029/2018GL079150
- ISSN
- 1944-8007
- eISSN
- 1944-8007
- Grant note
- DOI: 10.13039/501100001859, name: Swedish National Space Board; DOI: 10.13039/501100001859, name: Swedish National Space Board, award: Dnr 174/15, Dnr 135/13, 621-2013-4191; DOI: 10.13039/100000104, name: National Aeronautics and Space Administration, award: NNX16AI34G; DOI: 10.13039/100006196, name: Jet Propulsion Laboratory
- Language
- English
- Date published
- 10/16/2018
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984455544202771
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