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Suprathermal Magnetospheric Atomic and Molecular Heavy Ions At and Near Earth, Jupiter, and Saturn: Observations and Identification
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  • Stephen Christon,
  • Douglas Hamilton,
  • Donald Mitchell,
  • John Plane,
  • Stuart Nylund
Stephen Christon
Focused Analysis and Research

Corresponding Author:spchriston@aol.com

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Douglas Hamilton
University of Maryland
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Donald Mitchell
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John Plane
University of Leeds
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Stuart Nylund
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We compare the long-term suprathermal heavy ion composition measured at three planets using functionally identical charge-energy-mass ion spectrometers, one on Geotail, orbiting Earth at ~9-30 Re, the other on Cassini, in interplanetary space, during Jupiter flyby, and then in orbit around Saturn. O+, a principal suprathermal (~80-220 keV/e) heavy ion in each magnetosphere, derives primarily from outflowing ionospheric O+ at Earth, but mostly from satellites and rings at Jupiter and Saturn. Comparable amounts of Iogenic O+ and S+ are present at Jupiter. Ions escaping the magnetospheres are: O+ and S+ at Jupiter; C+, N+, O+, H2O+, CO+(N2+), and O2+ at Saturn; and N+, O+, N2+, NO+, O2+, and Fe+ at Earth. Generally, escaped atomic ions (molecular ions, MI) at Earth and Saturn have similar (higher) ratios to O+ compared to their magnetospheric ratios; Saturn’s H2O+ and Fe+ ratios are lower. At Earth: after O+ and N+, ionospheric origin N2+, NO+, and O2+ (with proportions ~0.9:1.0:0.2) dominate magnetospheric heavy ions, consistent with recent high-altitude/latitude ionospheric measurements and models; average ion count rates correlate positively with geomagnetic and solar activity. At ~27-33 amu/e: Earth’s MIs dominate over lunar pickup ions (PUIs) in the magnetosphere; MIs are roughly comparable to lunar PUIs in the magnetosheath; and lunar PUIs dominate over MIs beyond Earth’s bow shock. Lunar PUIs are detected at ~39-48 amu/e in the lobe and possibly in the plasma sheet at very low levels.
Jan 2020Published in Journal of Geophysical Research: Space Physics volume 125 issue 1. 10.1029/2019JA027271