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  Seasonal and Hemispheric Asymmetries of F Region Polar Cap Plasma Density: Swarm and CHAMP Observations

Hatch, S. M., Haaland, S., Laundal, K. M., Moretto, T., Yau, A. W., Bjoland, L., et al. (2020). Seasonal and Hemispheric Asymmetries of F Region Polar Cap Plasma Density: Swarm and CHAMP Observations. Journal of Geophysical Research: Space Physics, 125(11): e2020JA028084. doi:10.1029/2020JA028084.

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 Creators:
Hatch, S. M., Author
Haaland, Stein1, Author              
Laundal, K. M., Author
Moretto, T., Author
Yau, A. W., Author
Bjoland, L., Author
Reistad, J. P., Author
Ohma, A., Author
Oksavik, K., Author
Affiliations:
1Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832288              

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 MPIS_PROJECTS: Cluster
 Abstract: One of the primary mechanisms of loss of Earth's atmosphere is the persistent “cold” (T <20eV) ion outflow that has been observed in the magnetospheric lobes over large volumes with dimensions of order several Earth radii. As the main source of this cold ion outflow, the polar cap F region ionosphere and conditions within it have a disproportionate influence on these magnetospheric regions. Using 15 years of measurements of plasma density Ne made by the Swarm spacecraft constellation and the Challenging Mini Satellite Payload (CHAMP) spacecraft within the F region of the polar cap above 80° Apex magnetic latitude, we report evidence of several types of seasonal asymmetries in polar cap Ne. Among these, the transition between “winter‐like” and “summer‐like” median polar cap Ne occurs 1 week prior to local spring equinox in the Northern Hemisphere (NH) and 1 week after local spring equinox in the Southern Hemisphere (SH). Thus, the median SH polar cap Ne lags the median NH polar cap Ne by approximately 2 weeks with respect to hemispherically local spring and fall equinox. From interhemispheric comparison of statistical distributions of polar cap plasma density around each equinox and solstice, we find that distributions in the SH are often flatter (i.e., less skewed and kurtotic) than those in the NH. Perhaps of most significance to cold ion outflow, we find no evidence of an F region plasma density counterpart to a previously reported hemispheric asymmetry whereby cold plasma density is higher in the NH magnetospheric lobe than in the SH lobe.

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Language(s): eng - English
 Dates: 2020
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1029/2020JA028084
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Title: Journal of Geophysical Research: Space Physics
  Other : JGR-A
  Abbreviation : J. Geophys. Res. - A
Source Genre: Journal
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Publ. Info: Washington, D.C. : American Geophysical Union
Pages: - Volume / Issue: 125 (11) Sequence Number: e2020JA028084 Start / End Page: - Identifier: ISSN: 0148-0227
CoNE: https://pure.mpg.de/cone/journals/resource/991042728714264