Limits...
Upper limit on the inner radiation belt MeV electron intensity.

Li X, Selesnick RS, Baker DN, Jaynes AN, Kanekal SG, Schiller Q, Blum L, Fennell J, Blake JB - J Geophys Res Space Phys (2015)

Bottom Line: For 1.7, 2.5, and 3.3 MeV electrons, the upper limits are about 1 order of magnitude lower than predicted model fluxes.The implication of this difference is profound in that unless there are extreme solar wind conditions, which have not happened yet since the launch of Van Allen Probes, significant enhancements of MeV electrons do not occur in the inner belt even though such enhancements are commonly seen in the outer belt.Quantified upper limit of MeV electrons in the inner beltActual MeV electron intensity likely much lower than the upper limitMore detailed understanding of relativistic electrons in the magnetosphere.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado Boulder Boulder, Colorado, USA ; Department of Aerospace Engineering Sciences, University of Colorado Boulder Boulder, Colorado, USA.

ABSTRACT

: No instruments in the inner radiation belt are immune from the unforgiving penetration of the highly energetic protons (tens of MeV to GeV). The inner belt proton flux level, however, is relatively stable; thus, for any given instrument, the proton contamination often leads to a certain background noise. Measurements from the Relativistic Electron and Proton Telescope integrated little experiment on board Colorado Student Space Weather Experiment CubeSat, in a low Earth orbit, clearly demonstrate that there exist sub-MeV electrons in the inner belt because their flux level is orders of magnitude higher than the background, while higher-energy electron (>1.6 MeV) measurements cannot be distinguished from the background. Detailed analysis of high-quality measurements from the Relativistic Electron and Proton Telescope on board Van Allen Probes, in a geo-transfer-like orbit, provides, for the first time, quantified upper limits on MeV electron fluxes in various energy ranges in the inner belt. These upper limits are rather different from flux levels in the AE8 and AE9 models, which were developed based on older data sources. For 1.7, 2.5, and 3.3 MeV electrons, the upper limits are about 1 order of magnitude lower than predicted model fluxes. The implication of this difference is profound in that unless there are extreme solar wind conditions, which have not happened yet since the launch of Van Allen Probes, significant enhancements of MeV electrons do not occur in the inner belt even though such enhancements are commonly seen in the outer belt.

Key points: Quantified upper limit of MeV electrons in the inner beltActual MeV electron intensity likely much lower than the upper limitMore detailed understanding of relativistic electrons in the magnetosphere.

No MeSH data available.


Related in: MedlinePlus

Similar to Figure 6 but from PHA data in Ranges 2 through 5 only.
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fig07: Similar to Figure 6 but from PHA data in Ranges 2 through 5 only.

Mentions: Van Allen Probes satellites are oriented such that the spin axis is roughly in the sunward direction, with a spin period of ∼12 s. Directional differential intensity, from PHA events nominally identified as electrons, is shown in the form of equatorial pitch angle distributions (PADs) at selected L and E values in Figures 6 and 7. Data are from REPT-A and REPT-B data combined and averaged over a 6 day interval (3–8 October 2013). Figure 6 includes data from Ranges 1 to 5 events; Figure 7 includes only Ranges 2 to 5 events but uses the efficiency from Figure 5b (Figure 4b gives essentially the same efficiency) as a correction factor for the lower energies. For the lower energies, E = 1.7, 2.5, and 3.3 MeV, Figure 6 includes the Range 1 data but Figure 7 does not. The smaller number of events used in Figure 7 is combined with a smaller efficiency factor to determine electron intensities, which should thereby agree with those of Figure 6.


Upper limit on the inner radiation belt MeV electron intensity.

Li X, Selesnick RS, Baker DN, Jaynes AN, Kanekal SG, Schiller Q, Blum L, Fennell J, Blake JB - J Geophys Res Space Phys (2015)

Similar to Figure 6 but from PHA data in Ranges 2 through 5 only.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4497489&req=5

fig07: Similar to Figure 6 but from PHA data in Ranges 2 through 5 only.
Mentions: Van Allen Probes satellites are oriented such that the spin axis is roughly in the sunward direction, with a spin period of ∼12 s. Directional differential intensity, from PHA events nominally identified as electrons, is shown in the form of equatorial pitch angle distributions (PADs) at selected L and E values in Figures 6 and 7. Data are from REPT-A and REPT-B data combined and averaged over a 6 day interval (3–8 October 2013). Figure 6 includes data from Ranges 1 to 5 events; Figure 7 includes only Ranges 2 to 5 events but uses the efficiency from Figure 5b (Figure 4b gives essentially the same efficiency) as a correction factor for the lower energies. For the lower energies, E = 1.7, 2.5, and 3.3 MeV, Figure 6 includes the Range 1 data but Figure 7 does not. The smaller number of events used in Figure 7 is combined with a smaller efficiency factor to determine electron intensities, which should thereby agree with those of Figure 6.

Bottom Line: For 1.7, 2.5, and 3.3 MeV electrons, the upper limits are about 1 order of magnitude lower than predicted model fluxes.The implication of this difference is profound in that unless there are extreme solar wind conditions, which have not happened yet since the launch of Van Allen Probes, significant enhancements of MeV electrons do not occur in the inner belt even though such enhancements are commonly seen in the outer belt.Quantified upper limit of MeV electrons in the inner beltActual MeV electron intensity likely much lower than the upper limitMore detailed understanding of relativistic electrons in the magnetosphere.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Atmospheric and Space Physics, University of Colorado Boulder Boulder, Colorado, USA ; Department of Aerospace Engineering Sciences, University of Colorado Boulder Boulder, Colorado, USA.

ABSTRACT

: No instruments in the inner radiation belt are immune from the unforgiving penetration of the highly energetic protons (tens of MeV to GeV). The inner belt proton flux level, however, is relatively stable; thus, for any given instrument, the proton contamination often leads to a certain background noise. Measurements from the Relativistic Electron and Proton Telescope integrated little experiment on board Colorado Student Space Weather Experiment CubeSat, in a low Earth orbit, clearly demonstrate that there exist sub-MeV electrons in the inner belt because their flux level is orders of magnitude higher than the background, while higher-energy electron (>1.6 MeV) measurements cannot be distinguished from the background. Detailed analysis of high-quality measurements from the Relativistic Electron and Proton Telescope on board Van Allen Probes, in a geo-transfer-like orbit, provides, for the first time, quantified upper limits on MeV electron fluxes in various energy ranges in the inner belt. These upper limits are rather different from flux levels in the AE8 and AE9 models, which were developed based on older data sources. For 1.7, 2.5, and 3.3 MeV electrons, the upper limits are about 1 order of magnitude lower than predicted model fluxes. The implication of this difference is profound in that unless there are extreme solar wind conditions, which have not happened yet since the launch of Van Allen Probes, significant enhancements of MeV electrons do not occur in the inner belt even though such enhancements are commonly seen in the outer belt.

Key points: Quantified upper limit of MeV electrons in the inner beltActual MeV electron intensity likely much lower than the upper limitMore detailed understanding of relativistic electrons in the magnetosphere.

No MeSH data available.


Related in: MedlinePlus