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| Titel |
Visualizing the Invisible and Other Wonders of Saturn' s Magnetosphere |
| VerfasserIn |
Stamatios Krimigis, Donald Mitchell, Norbert Krupp, Douglas Hamilton, Jannis Dandouras |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093843
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| Publikation (Nr.) |
 EGU/EGU2014-8961.pdf |
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| Zusammenfassung |
| New measurement capabilities on exploratory missions always make new discoveries and
reveal new phenomena, even when earlier planetary encounters had sketched out the broad
features of a planet’ s environment. And so it is with the Cassini-Huygens intensive study of
the Saturn system, even though the reconnaissance of the planet had already taken place first
with Pioneer-11 in 1979 and then Voyager-1 and -2 in 1980 and 1981, respectively. Thus, the
inclusion in the payload of the Ion and Neutral Camera (INCA) to perform energetic neutral
atom (ENA) imaging, plus an instrument that could measure ion charge state (CHEMS) and,
in addition, state-of-the-art electron and ion sensors (LEMMS) provided the tools for a
plethora of new and unique observations. These include, but are not limited to: (1)
explosive large-scale injections appearing beyond 12 RS in the post-midnight sector,
propagate inward, are connected to auroral brightening and SKR emissions, and
apparently local injections as far in as 6 RS in the pre-midnight through post-midnight
sector with a recurrence period around 11h that appear to corotate past noon; (2)
periodicities in energetic charged particles in Saturn’ s magnetosphere, including "dual"
periodicities, their slow variations, periodic tilting of the plasma sheet, , and the possible
explanation of these periodicities by a "wavy" magnetodisk model and the existence
of the solar wind "driver" periodicity at ~26 days; (3) dominance of water group
(W+) and H+ with a healthy dose of H2+ ions in the energetic particle population
throughout the middle magnetosphere, plus minor species such as O2+ and 28M+ of
unknown origin, all with relative abundances varying with the solar cycle and/or
Saturn’ s seasons; (4) sudden increases in energetic ion intensity around Saturn,
in the vicinity of the moons Dione and Tethys, each lasting for several weeks, in
response to interplanetary events caused by solar eruptions.; (5) a uniform electric
field of around 0.11-0.18 mV/m within 4.4-7.0 RS oriented roughly from noon to
midnight, that explains the persistent radial offsets of satellite electron microsignatures
from their expected positions; (6) determination that the ring current pressure in the
outer magnetosphere is dominated by superthermal ions heavier than protons; (7)
detection of magnetic-field-aligned ion and electron beams (offset several moon radii
downstream from Enceladus) with sufficient power to stimulate detectable aurora, and
the subsequent discovery of Enceladus-associated aurora in a few per cent of the
scans of the moon’ s footprint. These and many other observations have revealed
fundamental plasma processes operating in Saturn’ s magnetosphere such as magnetotail
reconnection, centrifugal interchange instability, ion and electron acceleration,
convection/diffusion, charge exchange, and magnetosphere/ionosphere coupling, among
others. |
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