Christon, SP, Hamilton, DC, Plane, JMC orcid.org/0000-0003-3648-6893 et al. (4 more authors) (2017) Discovery of Suprathermal Ionospheric Origin Fe⁺ in and Near Earth's Magnetosphere. Journal of Geophysical Research: Space Physics, 122 (11). pp. 11175-11200. ISSN 2169-9380
Abstract
Suprathermal (87–212 keV/e) singly charged iron, Fe⁺, has been discovered in and near Earth's ~9–30 RE equatorial magnetosphere using ~21 years of Geotail STICS (suprathermal ion composition spectrometer) data. Its detection is enhanced during higher geomagnetic and solar activity levels. Fe⁺, rare compared to dominant suprathermal solar wind and ionospheric origin heavy ions, might derive from one or all three candidate lower‐energy sources: (a) ionospheric outflow of Fe⁺ escaped from ion layers near ~100 km altitude, (b) charge exchange of nominal solar wind iron, Fe⁺≥⁷, in Earth's exosphere, or (c) inner source pickup Fe⁺ carried by the solar wind, likely formed by solar wind Fe interaction with near‐Sun interplanetary dust particles. Earth's semipermanent ionospheric Fe⁺ layers derive from tons of interplanetary dust particles entering Earth's atmosphere daily, and Fe⁺ scattered from these layers is observed up to ~1000 km altitude, likely escaping in strong ionospheric outflows. Using ~26% of STICS's magnetosphere‐dominated data when possible Fe⁺² ions are not masked by other ions, we demonstrate that solar wind Fe charge exchange secondaries are not an obvious Fe⁺ source. Contemporaneous Earth flyby and cruise data from charge‐energy‐mass spectrometer on the Cassini spacecraft, a functionally identical instrument, show that inner source pickup Fe⁺ is likely not important at suprathermal energies. Consequently, we suggest that ionospheric Fe⁺ constitutes at least a significant portion of Earth's suprathermal Fe⁺, comparable to the situation at Saturn where suprathermal Fe⁺ is also likely of ionospheric origin.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017. American Geophysical Union. This is the peer reviewed version of the following article: Christon, S. P., Hamilton, D. C., Plane, J. M. C., Mitchell, D. G., Grebowsky, J. M., Spjeldvik, W. N., & Nylund, S. R. (2017). Discovery of suprathermal ionospheric origin Fe+ in and near Earth's magnetosphere. Journal of Geophysical Research: Space Physics, 122, 11,175–11,200. https://doi.org/10.1002/2017JA024414, which has been published in final form at https://doi.org/10.1002/2017JA024414. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | magnetosphere; ionosphere; energetic particles; dust |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 05 Sep 2017 15:32 |
Last Modified: | 21 Mar 2018 16:39 |
Status: | Published |
Publisher: | Wiley |
Identification Number: | 10.1002/2017JA024414 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:120820 |