학술논문
Dynamics of Saturn's magnetosphere from MIMI during Cassini's orbital insertion
Document Type
Academic Journal
Author
Krimigis, S.M.; Mitchell, D.G.; Hamilton, D.C.; Krupp, N.; Livi, S.; Roelof, E.C.; Dandouras, J.; Armstrong, T.P.; Mauk, B.H.; Paranicas, C.; Brandt, P.C.; Bolton, S.; Cheng, A.F.; Choo, T.; Gloeckler, G.; Hayes, J.; Hsieh, K.C.; Ip, W.-H.; Jaskulek, S.; Keath, E.P.; Kirsch, E.; Kusterer, M.; Lagg, A.; Lanzerotti, L.J.; LaVallee, D.; Manweiler, J.; McEntire, R.W.; Rasmuss, W.; Saur, J.; Turner, F.S.; Williams, D.J.; Woch, J.
Source
Science. February 25, 2005, Vol. 307 Issue 5713, p1270, 4 p.
Subject
Language
English
ISSN
0036-8075
Abstract
The Magnetospheric Imaging Instrument (MIMI) onboard the Cassini spacecraft observed the saturnian magnetosphere from January 2004 until Saturn orbit insertion (SOI) on 1 July 2004. The MIMI sensors observed frequent energetic particle activity in interplanetary space for several months before SOI. When the imaging sensor was switched to its energetic neutral atom (ENA) operating mode on 20 February 2004, at ~[10.sup.3] times Saturn's radius [R.sub.S] (0.43 astronomical units), a weak but persistent signal was observed from the magnetosphere. About 10 days before SOI, the magnetosphere exhibited a day-night asymmetry that varied with an ~11-hour periodicity. Once Cassini entered the magnetosphere, in situ measurements showed high concentrations of [H.sup.+], [H.sub.2.sup.+], [O.sup.+], O[H.sup.+], and [H.sub.2][O.sup.+] and low concentrations of [N.sup.+]. The radial dependence of ion intensity profiles implies neutral gas densities sufficient to produce high loss rates of trapped ions from the middle and inner magnetosphere. ENA imaging has revealed a radiation belt that resides inward of the D ring and is probably the result of double charge exchange between the main radiation belt and the upper layers of Saturn's exosphere.
The magnetosphere of Saturn was discovered by Pioneer 11 in 1979 (1, 2) and was investigated in detail by Voyager 1 in 1980 (3) and Voyager 2 in 1981 (4). [...]
The magnetosphere of Saturn was discovered by Pioneer 11 in 1979 (1, 2) and was investigated in detail by Voyager 1 in 1980 (3) and Voyager 2 in 1981 (4). [...]