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Title: The hidden dynamics of relativistic electrons (0.7-1.5 MeV) in the inner zone and slot region

Abstract

We present measurements of relativistic electrons (0.7–1.5 MeV) in the inner zone and slot region obtained by the Magnetic Electron and Ion Spectrometer (MagEIS) instrument on Van Allen Probes. The data presented are corrected for background contamination, which is primarily due to inner-belt protons in these low-L regions. We find that ~1 MeV electrons were transported into the inner zone following the two largest geomagnetic storms of the Van Allen Probes era to date, the March and June 2015 events. As ~1 MeV electrons were not observed in Van Allen Probes data in the inner zone prior to these two events, the injections created a new inner belt that persisted for at least 1.5 years. In contrast, we find that electrons injected into the slot region decay on much faster timescales, approximately tens of days. Furthermore, we find no evidence of >1.5 MeV electrons in the inner zone during the entire time interval considered (April 2013 through September 2016). The energies we examine thus span a transition range in the steeply falling inner zone electron spectrum, where modest intensities are observed at 0.7 MeV, and no electrons are observed at 1.5 MeV. To validate the results obtained from the backgroundmore » corrected flux measurements, we also present detailed pulse-height spectra from individual MagEIS detectors. These measurements confirm our results and also reveal low-intensity inner zone and slot region electrons that are not captured in the standard background corrected data product. Lastly, we briefly discuss efforts to refine the upper limit of inner zone MeV electron flux obtained in earlier work.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]
  1. The Aerospace Corp., El Segundo, CA (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Univ. of New Hampshire, Durham, NH (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
National Aeronautic and Space Administration (NASA); USDOE
OSTI Identifier:
1351198
Report Number(s):
LA-UR-17-20109
Journal ID: ISSN 2169-9380
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Space Physics
Additional Journal Information:
Journal Volume: 122; Journal Issue: 3; Journal ID: ISSN 2169-9380
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Heliospheric and Magnetospheric Physics

Citation Formats

Claudepierre, Seth G., O'Brien, T. P., Fennell, J. F., Blake, J. B., Clemmons, J. H., Looper, M. D., Mazur, J. E., Roeder, J. L., Turner, D. L., Reeves, Geoffrey D., and Spence, H. E. The hidden dynamics of relativistic electrons (0.7-1.5 MeV) in the inner zone and slot region. United States: N. p., 2017. Web. doi:10.1002/2016JA023719.
Claudepierre, Seth G., O'Brien, T. P., Fennell, J. F., Blake, J. B., Clemmons, J. H., Looper, M. D., Mazur, J. E., Roeder, J. L., Turner, D. L., Reeves, Geoffrey D., & Spence, H. E. The hidden dynamics of relativistic electrons (0.7-1.5 MeV) in the inner zone and slot region. United States. doi:10.1002/2016JA023719.
Claudepierre, Seth G., O'Brien, T. P., Fennell, J. F., Blake, J. B., Clemmons, J. H., Looper, M. D., Mazur, J. E., Roeder, J. L., Turner, D. L., Reeves, Geoffrey D., and Spence, H. E. Wed . "The hidden dynamics of relativistic electrons (0.7-1.5 MeV) in the inner zone and slot region". United States. doi:10.1002/2016JA023719. https://www.osti.gov/servlets/purl/1351198.
@article{osti_1351198,
title = {The hidden dynamics of relativistic electrons (0.7-1.5 MeV) in the inner zone and slot region},
author = {Claudepierre, Seth G. and O'Brien, T. P. and Fennell, J. F. and Blake, J. B. and Clemmons, J. H. and Looper, M. D. and Mazur, J. E. and Roeder, J. L. and Turner, D. L. and Reeves, Geoffrey D. and Spence, H. E.},
abstractNote = {We present measurements of relativistic electrons (0.7–1.5 MeV) in the inner zone and slot region obtained by the Magnetic Electron and Ion Spectrometer (MagEIS) instrument on Van Allen Probes. The data presented are corrected for background contamination, which is primarily due to inner-belt protons in these low-L regions. We find that ~1 MeV electrons were transported into the inner zone following the two largest geomagnetic storms of the Van Allen Probes era to date, the March and June 2015 events. As ~1 MeV electrons were not observed in Van Allen Probes data in the inner zone prior to these two events, the injections created a new inner belt that persisted for at least 1.5 years. In contrast, we find that electrons injected into the slot region decay on much faster timescales, approximately tens of days. Furthermore, we find no evidence of >1.5 MeV electrons in the inner zone during the entire time interval considered (April 2013 through September 2016). The energies we examine thus span a transition range in the steeply falling inner zone electron spectrum, where modest intensities are observed at 0.7 MeV, and no electrons are observed at 1.5 MeV. To validate the results obtained from the background corrected flux measurements, we also present detailed pulse-height spectra from individual MagEIS detectors. These measurements confirm our results and also reveal low-intensity inner zone and slot region electrons that are not captured in the standard background corrected data product. Lastly, we briefly discuss efforts to refine the upper limit of inner zone MeV electron flux obtained in earlier work.},
doi = {10.1002/2016JA023719},
journal = {Journal of Geophysical Research. Space Physics},
number = 3,
volume = 122,
place = {United States},
year = {Wed Mar 15 00:00:00 EDT 2017},
month = {Wed Mar 15 00:00:00 EDT 2017}
}

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  • Here, we present observations of the radiation belts from the Helium Oxygen Proton Electron and Magnetic Electron Ion Spectrometer particle detectors on the Van Allen Probes satellites that illustrate the energy dependence and L shell dependence of radiation belt enhancements and decays. We survey events in 2013 and analyze an event on 1 March in more detail. The observations show the following: (a) at all L shells, lower energy electrons are enhanced more often than higher energies; (b) events that fill the slot region are more common at lower energies; (c) enhancements of electrons in the inner zone are moremore » common at lower energies; and (d) even when events do not fully fill the slot region, enhancements at lower energies tend to extend to lower L shells than higher energies. During enhancement events the outer zone extends to lower L shells at lower energies while being confined to higher L shells at higher energies. The inner zone shows the opposite with an outer boundary at higher L shells for lower energies. Both boundaries are nearly straight in log(energy) versus L shell space. At energies below a few 100 keV, radiation belt electron penetration through the slot region into the inner zone is commonplace, but the number and frequency of “slot filling” events decreases with increasing energy. The inner zone is enhanced only at energies that penetrate through the slot. Energy- and L shell-dependent losses (that are consistent with whistler hiss interactions) return the belts to more quiescent conditions.« less
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  • An investigation has been made of the local time morphology of electron (>130 keV) precipitation from the slot region of the radiation belts. Quasi- trapped electrons (h/sub min/<0) were observed just east of the South Atlantic anomaly at low altitudes (approx.800 km) from the satellite 1971-089A. On the average, the fluxes of electrons precipitating in the daytime are greater than those near midnight, consistent with the findings of Vampola et al. In addition, shortly after 0800 hours MLT there is a pronounced increase in the frequency of occurrence of peaks in the energy spectra. These peaks have central energies thatmore » decrease rapidly with increasing L value. The data reveal that the electron loss processes are more effective during the daytime than near midnight and that there may be basic differences in the nature of the precipitation mechanisms at the two times. (AIP)« less