TY - JOUR

T1 - Energy-banded ions in Saturn's magnetosphere

AU - Thomsen, M. F.

AU - Badman, Sarah Victoria

AU - Jackman, Caitriona M.

AU - Jia, X.

AU - Kivelson, Margaret G.

AU - Kurth, W.S.

N1 - An edited version of this paper was published by AGU. Copyright 2016 American Geophysical Union. Copyright 2017 American Geophysical Union. Further reproduction or electronic distribution is not permitted. Thomsen, M. F., S. V. Badman, C. M. Jackman, X. Jia, M. G. Kivelson, and W. S. Kurth (2017), Energy-banded ions in Saturn's magnetosphere, J. Geophys. Res. Space Physics, 122, doi:10.1002/2017JA024147

PY - 2017/5

Y1 - 2017/5

N2 - Using data from the Cassini Plasma Spectrometer ion mass spectrometer, we report the first observation of energy-banded ions at Saturn. Observed near midnight at relatively high magnetic latitudes, the banded ions are dominantly H+, and they occupy the range of energies typically associated with the thermal pickup distribution in the inner magnetosphere (L < 10), but their energies decline monotonically with increasing radial distance (or time or decreasing latitude). Their pitch angle distribution suggests a source at low (or slightly southern) latitudes. The band energies, including their pitch angle dependence, are consistent with a bounce-resonant interaction between thermal H+ ions and the standing wave structure of a field line resonance. There is additional evidence in the pitch angle dependence of the band energies that the particles in each band may have a common time of flight from their most recent interaction with the wave, which may have been at slightly southern latitudes. Thus, while the particles are basically bounce resonant, their energization may be dominated by their most recent encounter with the standing wave.

AB - Using data from the Cassini Plasma Spectrometer ion mass spectrometer, we report the first observation of energy-banded ions at Saturn. Observed near midnight at relatively high magnetic latitudes, the banded ions are dominantly H+, and they occupy the range of energies typically associated with the thermal pickup distribution in the inner magnetosphere (L < 10), but their energies decline monotonically with increasing radial distance (or time or decreasing latitude). Their pitch angle distribution suggests a source at low (or slightly southern) latitudes. The band energies, including their pitch angle dependence, are consistent with a bounce-resonant interaction between thermal H+ ions and the standing wave structure of a field line resonance. There is additional evidence in the pitch angle dependence of the band energies that the particles in each band may have a common time of flight from their most recent interaction with the wave, which may have been at slightly southern latitudes. Thus, while the particles are basically bounce resonant, their energization may be dominated by their most recent encounter with the standing wave.

U2 - 10.1002/2017JA024147

DO - 10.1002/2017JA024147

M3 - Journal article

VL - 122

SP - 5181

EP - 5202

JO - Journal of Geophysical Research: Space Physics

JF - Journal of Geophysical Research: Space Physics

SN - 2169-9402

IS - 5

ER -