Document Type

Article

Publication Title

Journal of Geophysical Research: Space Physics

Publisher

American Geophysical Union Publications

Publication Date

11-7-2014

Volume

119

Disciplines

Astrophysics and Astronomy | Physical Sciences and Mathematics

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 ration, 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.

Keywords

Saturn, magnetosphere, interchange, injection, ion composition

DOI

10.1002/2014JA020489

Comments

An edited version of this paper was published by AGU. Copyright (2014) American Geophysical Union.

Rights

© 2014. American Geophysical Union. All Rights Reserved.

Download

Share

COinS