Discovery of Suprathermal Fe+ in the Magnetospheres of Earth and Saturn

Stephen P Christon1, Dr. Douglas Stephen Hamilton2, Donald G Mitchell3, John M C Plane4, Robert D DiFabio5, Stamatios Mike Krimigis6,7, Stuart R Nylund7 and Anthony Lui7, (1)Focused Analysis and Research, Columbia, MD, United States, (2)North Carolina State University, Marine, Earth, and Atmospheric Sciences, Raleigh, United States, (3)Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States, (4)University of Leeds, School of Chemistry, Leeds, United Kingdom, (5)University of Louisiana, Department of Physics, Lafayette, LA, United States, (6)Johns Hopkins University Applied Physics Laboratory, Laurel, United States, (7)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States
Abstract:
We compare measurements from two similar ion spectrometers to report on the first observations of suprathermal Fe+ in the magnetospheres of Earth and Saturn at tens to hundreds of keV/e. Geotail/EPIC/STICS has measured ions at Earth since late-1992 and Cassini/MIMI/CHEMS has measured ions at Saturn since mid-2004. The 56 amu/e singly-charged Fe+ ions are rare in both magnetospheres and easily identified in long-term averages. At Earth, the long-term averages also reveal N+, O+, N2+, and NO+ ions, which, to our knowledge, likely only originate in Earth's lower ionosphere and escape primarily during disturbed geomagnetic intervals. At Saturn, the Fe+ displays a distinct spatial variation and may originate from either of two possible sources - ionospheric escape as at Earth and/or meteoric materials embedded in Saturn's main rings. We will compare and contrast aspects of the observations at the two planets.
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