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Ion composition in interchange injection events in Saturn's magnetosphere

Ion composition in interchange injection events in Saturn's magnetosphere
Ion composition in interchange injection events in Saturn's magnetosphere

Interchange injection events are commonly observed by the Cassini spacecraft in the region between about 6 and 12 Rs (1 Rs = 60,268 km) and even frequently beyond. In this study, 13 examples of interchange injection events are identified in Cassini/Cassini Plasma Spectrometer data under special conditions such that time-of-flight (TOF) mass spectra could be obtained from entirely within the events. Using the TOF data to separate the main ion species H+, H2+, and W+, approximate densities of each species are calculated under the assumption that all distributions were isotropic. The light-ion density ratios, H2+/H+, in the injection events are not discernibly different from those ratios in control intervals from the ambient plasma. However, the water-group ratio, W+/H+, is significantly lower than ambient. The comparison of the measured density ratios with the range of values observed throughout Saturn's magnetosphere indicates that the values of W+/H+ that are as low as those observed within the injection events are found primarily beyond L~14 (where L is the equatorial crossing distance, in Saturn radius, of a dipole field line), indicating that the injection events are delivering plasma from the outer magnetosphere at times traveling at least 6 Rs.

injection, interchange, magnetosphere, Saturn
2169-9380
9761-9772
Thomsen, M. F.
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Reisenfeld, D. B.
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Wilson, R. J.
3eb91ab1-d5c4-4f0c-a5d1-8944b536a296
Andriopoulou, M.
70018ad1-b7db-4cd0-8d95-ad484b92e5b1
Crary, F. J.
43ea810b-5052-4341-854a-4a891f104051
Hospodarsky, G. B.
a8e798f4-dbcf-49c5-8e82-24c279fd6596
Jackman, C. M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Jia, X.
0b268c4d-354d-40fe-bf84-8618bed40f33
Khurana, K. K.
13e3a0d9-2a06-4bff-8a6a-7de9a4e304e2
Paranicas, C.
afafdeb4-2f93-4322-848f-f35eb7054fb0
Roussos, E.
6b85b964-976c-4bd0-b1aa-b2ba918482da
Sergis, N.
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Tokar, R. L.
8213ad4b-5b3b-46b1-90ad-334b61c2d79c
Thomsen, M. F.
bc09abeb-5d20-449f-9f54-568fff6d220c
Reisenfeld, D. B.
146943bf-0a2f-47a8-b1d3-208e2d0487b2
Wilson, R. J.
3eb91ab1-d5c4-4f0c-a5d1-8944b536a296
Andriopoulou, M.
70018ad1-b7db-4cd0-8d95-ad484b92e5b1
Crary, F. J.
43ea810b-5052-4341-854a-4a891f104051
Hospodarsky, G. B.
a8e798f4-dbcf-49c5-8e82-24c279fd6596
Jackman, C. M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Jia, X.
0b268c4d-354d-40fe-bf84-8618bed40f33
Khurana, K. K.
13e3a0d9-2a06-4bff-8a6a-7de9a4e304e2
Paranicas, C.
afafdeb4-2f93-4322-848f-f35eb7054fb0
Roussos, E.
6b85b964-976c-4bd0-b1aa-b2ba918482da
Sergis, N.
3b07fcbf-eb7f-496c-9b8d-c4f21fc9f87b
Tokar, R. L.
8213ad4b-5b3b-46b1-90ad-334b61c2d79c

Thomsen, M. F., Reisenfeld, D. B., Wilson, R. J., Andriopoulou, M., Crary, F. J., Hospodarsky, G. B., Jackman, C. M., Jia, X., Khurana, K. K., Paranicas, C., Roussos, E., Sergis, N. and Tokar, R. L. (2014) Ion composition in interchange injection events in Saturn's magnetosphere. Journal of Geophysical Research: Space Physics, 119 (12), 9761-9772. (doi:10.1002/2014JA020489).

Record type: Article

Abstract

Interchange injection events are commonly observed by the Cassini spacecraft in the region between about 6 and 12 Rs (1 Rs = 60,268 km) and even frequently beyond. In this study, 13 examples of interchange injection events are identified in Cassini/Cassini Plasma Spectrometer data under special conditions such that time-of-flight (TOF) mass spectra could be obtained from entirely within the events. Using the TOF data to separate the main ion species H+, H2+, and W+, approximate densities of each species are calculated under the assumption that all distributions were isotropic. The light-ion density ratios, H2+/H+, in the injection events are not discernibly different from those ratios in control intervals from the ambient plasma. However, the water-group ratio, W+/H+, is significantly lower than ambient. The comparison of the measured density ratios with the range of values observed throughout Saturn's magnetosphere indicates that the values of W+/H+ that are as low as those observed within the injection events are found primarily beyond L~14 (where L is the equatorial crossing distance, in Saturn radius, of a dipole field line), indicating that the injection events are delivering plasma from the outer magnetosphere at times traveling at least 6 Rs.

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More information

e-pub ahead of print date: 7 November 2014
Keywords: injection, interchange, magnetosphere, Saturn

Identifiers

Local EPrints ID: 436459
URI: http://eprints.soton.ac.uk/id/eprint/436459
ISSN: 2169-9380
PURE UUID: 9b967b59-7082-4c90-b091-4af1cf2828f4
ORCID for R. J. Wilson: ORCID iD orcid.org/0000-0002-5705-6078
ORCID for C. M. Jackman: ORCID iD orcid.org/0000-0003-0635-7361

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Date deposited: 11 Dec 2019 17:30
Last modified: 27 Jan 2020 13:46

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Contributors

Author: M. F. Thomsen
Author: D. B. Reisenfeld
Author: R. J. Wilson ORCID iD
Author: M. Andriopoulou
Author: F. J. Crary
Author: G. B. Hospodarsky
Author: C. M. Jackman ORCID iD
Author: X. Jia
Author: K. K. Khurana
Author: C. Paranicas
Author: E. Roussos
Author: N. Sergis
Author: R. L. Tokar

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