Saturn's Plasma Density Depletions Along Magnetic Field Lines Connected to the Main Rings
Abstract We report on a set of clear and abrupt decreases in the high‐frequency boundary of whistler mode emissions detected by Cassini at high latitudes (about ±40°) during the low‐altitude proximal flybys of Saturn. These abrupt decreases or dropouts have start and stop locations that correspond t...
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| Format: | Article |
| Language: | English |
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Wiley
2018-08-01
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| Series: | Geophysical Research Letters |
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| Online Access: | https://doi.org/10.1029/2018GL078137 |
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| author | W. M. Farrell L. Z. Hadid M. W. Morooka W. S. Kurth J.‐E. Wahlund R. J. MacDowall A. H. Sulaiman A. M. Persoon D. A. Gurnett |
| author_facet | W. M. Farrell L. Z. Hadid M. W. Morooka W. S. Kurth J.‐E. Wahlund R. J. MacDowall A. H. Sulaiman A. M. Persoon D. A. Gurnett |
| author_sort | W. M. Farrell |
| collection | DOAJ |
| description | Abstract We report on a set of clear and abrupt decreases in the high‐frequency boundary of whistler mode emissions detected by Cassini at high latitudes (about ±40°) during the low‐altitude proximal flybys of Saturn. These abrupt decreases or dropouts have start and stop locations that correspond to L shells at the edges of the A and B rings. Langmuir probe measurements can confirm, in some cases, that the abrupt decrease in the high‐frequency whistler mode boundary is associated with a corresponding abrupt electron density dropout over evacuated field lines connected to the A and B rings. Wideband data also reveal electron plasma oscillations and whistler mode cutoffs consistent with a low‐density plasma in the region. The observation of the electron density dropout along ring‐connecting field lines suggests that strong ambipolar forces are operating, drawing cold ionospheric ions outward to fill the flux tubes. There is an analog with the refilling of flux tubes in the terrestrial plasmasphere. We suggest that the ring‐connected electron density dropouts observed between 1.1 and 1.3 Rs are connected to the low‐density ring plasma cavity observed overtop the A and B rings during the 2004 Saturn orbital insertion pass. |
| format | Article |
| id | doaj-art-c40af852fa7c4b1c88d3518ba3b03486 |
| institution | DOAJ |
| issn | 0094-8276 1944-8007 |
| language | English |
| publishDate | 2018-08-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geophysical Research Letters |
| spelling | doaj-art-c40af852fa7c4b1c88d3518ba3b034862025-08-20T02:57:52ZengWileyGeophysical Research Letters0094-82761944-80072018-08-0145168104811010.1029/2018GL078137Saturn's Plasma Density Depletions Along Magnetic Field Lines Connected to the Main RingsW. M. Farrell0L. Z. Hadid1M. W. Morooka2W. S. Kurth3J.‐E. Wahlund4R. J. MacDowall5A. H. Sulaiman6A. M. Persoon7D. A. Gurnett8NASA Goddard Space Flight Center Greenbelt MD USASwedish Institute of Space Physics Uppsala SwedenSwedish Institute of Space Physics Uppsala SwedenDepartment of Physics and Astronomy University of Iowa Iowa City IA USASwedish Institute of Space Physics Uppsala SwedenNASA Goddard Space Flight Center Greenbelt MD USADepartment of Physics and Astronomy University of Iowa Iowa City IA USADepartment of Physics and Astronomy University of Iowa Iowa City IA USADepartment of Physics and Astronomy University of Iowa Iowa City IA USAAbstract We report on a set of clear and abrupt decreases in the high‐frequency boundary of whistler mode emissions detected by Cassini at high latitudes (about ±40°) during the low‐altitude proximal flybys of Saturn. These abrupt decreases or dropouts have start and stop locations that correspond to L shells at the edges of the A and B rings. Langmuir probe measurements can confirm, in some cases, that the abrupt decrease in the high‐frequency whistler mode boundary is associated with a corresponding abrupt electron density dropout over evacuated field lines connected to the A and B rings. Wideband data also reveal electron plasma oscillations and whistler mode cutoffs consistent with a low‐density plasma in the region. The observation of the electron density dropout along ring‐connecting field lines suggests that strong ambipolar forces are operating, drawing cold ionospheric ions outward to fill the flux tubes. There is an analog with the refilling of flux tubes in the terrestrial plasmasphere. We suggest that the ring‐connected electron density dropouts observed between 1.1 and 1.3 Rs are connected to the low‐density ring plasma cavity observed overtop the A and B rings during the 2004 Saturn orbital insertion pass.https://doi.org/10.1029/2018GL078137SaturnCassiniringsplasma |
| spellingShingle | W. M. Farrell L. Z. Hadid M. W. Morooka W. S. Kurth J.‐E. Wahlund R. J. MacDowall A. H. Sulaiman A. M. Persoon D. A. Gurnett Saturn's Plasma Density Depletions Along Magnetic Field Lines Connected to the Main Rings Geophysical Research Letters Saturn Cassini rings plasma |
| title | Saturn's Plasma Density Depletions Along Magnetic Field Lines Connected to the Main Rings |
| title_full | Saturn's Plasma Density Depletions Along Magnetic Field Lines Connected to the Main Rings |
| title_fullStr | Saturn's Plasma Density Depletions Along Magnetic Field Lines Connected to the Main Rings |
| title_full_unstemmed | Saturn's Plasma Density Depletions Along Magnetic Field Lines Connected to the Main Rings |
| title_short | Saturn's Plasma Density Depletions Along Magnetic Field Lines Connected to the Main Rings |
| title_sort | saturn s plasma density depletions along magnetic field lines connected to the main rings |
| topic | Saturn Cassini rings plasma |
| url | https://doi.org/10.1029/2018GL078137 |
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