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The relationship between the plasmapause and outer belt electrons
Journal article   Peer reviewed

The relationship between the plasmapause and outer belt electrons

J Goldstein, A. N Jaynes, C. A Kletzing, D. N Baker, J. B Blake, W. S Kurth, S De Pascuale, W Li, H. O Funsten, J.‐M Jahn, …
Journal of geophysical research. Space physics, Vol.121(9), pp.8392-8416
09/2016
DOI: 10.1002/2016JA023046
url
https://www.osti.gov/biblio/1325657View
Open Access

Abstract

We quantify the spatial relationship between the plasmapause and outer belt electrons for a 5 day period, 15–20 January 2013, by comparing locations of relativistic electron flux peaks to the plasmapause. A peak‐finding algorithm is applied to 1.8–7.7 MeV relativistic electron flux data. A plasmapause gradient finder is applied to wave‐derived electron number densities >10 cm−3. We identify two outer belts. Outer belt 1 is a stable zone of >3 MeV electrons located 1–2 RE inside the plasmapause. Outer belt 2 is a dynamic zone of <3 MeV electrons within 0.5 RE of the moving plasmapause. Electron fluxes earthward of each belt's peak are anticorrelated with cold plasma density. Belt 1 decayed on hiss timescales prior to a disturbance on 17 January and suffered only a modest dropout, perhaps owing to shielding by the plasmasphere. Afterward, the partially depleted belt 1 continued to decay at the initial rate. Belt 2 was emptied out by strong disturbance‐time losses but restored within 24 h. For global context we use a plasmapause test particle simulation and derive a new plasmaspheric index Fp, the fraction of a circular drift orbit inside the plasmapause. We find that the locally measured plasmapause is (for this event) a good proxy for the globally integrated opportunity for losses in cold plasma. Our analysis of the 15–20 January 2013 time interval confirms that high‐energy electron storage rings can persist for weeks or even months if prolonged quiet conditions prevail. This case study must be followed up by more general study (not limited to a 5 day period). Key Points Two outer belts, a dynamic zone near the plasmapause, and a stable zone deep within cold plasma Relativistic electron flux earthward of the peak is anticorrelated with dense plasma Electron lifetimes in stable outer belt are consistent with decay by plasmaspheric hiss
 plasmapause plasmaspheric hiss radiation belts simulation storm‐time dropouts Van Allen Probes

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