Equatorial Pitch Angle Distributions of 1-50 keV Electrons in Earth's Inner Magnetosphere: An Empirical Model Based on the Van Allen Probes Observations.
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| Title: | Equatorial Pitch Angle Distributions of 1-50 keV Electrons in Earth's Inner Magnetosphere: An Empirical Model Based on the Van Allen Probes Observations. |
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| Authors: | Zhao, H.1,2, Friedel, R. H. W.3, Chen, Y.3, Baker, D. N.1, Li, X.1, Malaspina, D. M.1, Larsen, B. A.3,4, Skoug, R. M.3, Funsten, H. O.3, Reeves, G. D.3,4, Boyd, A. J.5 |
| Source: | Journal of Geophysical Research. Space Physics. Jan2021, Vol. 126 Issue 1, p1-20. 20p. |
| Subject Terms: | *Van Allen radiation belts, Magnetosphere, Solar magnetism, Interplanetary medium, Interplanetary magnetic fields |
| Abstract: | Using 7 years of data from the Helium, Oxygen, Proton, and Electron instrument on the Van Allen Probes, equatorial pitch angle distributions (PADs) of 1-50 keV electrons in Earth's inner magnetosphere are investigated statistically. An empirical model of electron equatorial PADs as a function of radial distance, magnetic local time, geomagnetic activity, and electron energy is constructed using the method of Legendre polynomial fitting. Model results show that most equatorial PADs of 1-10s of keV electrons in Earth's inner magnetosphere are pancake PADs, and the lack of butterfly PADs is likely due to their relatively flat or positive flux radial gradients at higher altitudes. During geomagnetically quiet times, more anisotropic distributions of 1-10s of keV electrons at dayside than nightside are observed, which could be responsible for moderate chorus wave activities at dayside during quiet times as reported by previous studies. During active times, the anisotropy of 1-10s of keV electrons significantly enhances, consistent with the enhanced chorus wave activity during active times and suggesting the critical role of 1-10s of keV electrons in generating chorus waves in Earth's inner magnetosphere. Different enhanced anisotropy patterns of different energy electrons are also observed during active times: at R > ~4 RE, keV electrons are more anisotropic at dawn to noon, while 10s of keV electrons have larger anisotropy at midnight to dawn. These differences, combined with the statistical distribution of chorus waves shown in previous studies, suggest the differential roles of electrons with different energies in generating chorus waves with different properties. [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
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| Header | DbId: 8gh DbLabel: GreenFILE An: 148444484 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Equatorial Pitch Angle Distributions of 1-50 keV Electrons in Earth's Inner Magnetosphere: An Empirical Model Based on the Van Allen Probes Observations. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Zhao%2C+H%2E%22">Zhao, H.</searchLink><relatesTo>1,2</relatesTo><br /><searchLink fieldCode="AR" term="%22Friedel%2C+R%2E+H%2E+W%2E%22">Friedel, R. H. W.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Chen%2C+Y%2E%22">Chen, Y.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Baker%2C+D%2E+N%2E%22">Baker, D. N.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Li%2C+X%2E%22">Li, X.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Malaspina%2C+D%2E+M%2E%22">Malaspina, D. M.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Larsen%2C+B%2E+A%2E%22">Larsen, B. A.</searchLink><relatesTo>3,4</relatesTo><br /><searchLink fieldCode="AR" term="%22Skoug%2C+R%2E+M%2E%22">Skoug, R. M.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Funsten%2C+H%2E+O%2E%22">Funsten, H. O.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Reeves%2C+G%2E+D%2E%22">Reeves, G. D.</searchLink><relatesTo>3,4</relatesTo><br /><searchLink fieldCode="AR" term="%22Boyd%2C+A%2E+J%2E%22">Boyd, A. J.</searchLink><relatesTo>5</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Space+Physics%22">Journal of Geophysical Research. Space Physics</searchLink>. Jan2021, Vol. 126 Issue 1, p1-20. 20p. – Name: Subject Label: Subject Terms Group: Su Data: *<searchLink fieldCode="DE" term="%22Van+Allen+radiation+belts%22">Van Allen radiation belts</searchLink><br /><searchLink fieldCode="DE" term="%22Magnetosphere%22">Magnetosphere</searchLink><br /><searchLink fieldCode="DE" term="%22Solar+magnetism%22">Solar magnetism</searchLink><br /><searchLink fieldCode="DE" term="%22Interplanetary+medium%22">Interplanetary medium</searchLink><br /><searchLink fieldCode="DE" term="%22Interplanetary+magnetic+fields%22">Interplanetary magnetic fields</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Using 7 years of data from the Helium, Oxygen, Proton, and Electron instrument on the Van Allen Probes, equatorial pitch angle distributions (PADs) of 1-50 keV electrons in Earth's inner magnetosphere are investigated statistically. An empirical model of electron equatorial PADs as a function of radial distance, magnetic local time, geomagnetic activity, and electron energy is constructed using the method of Legendre polynomial fitting. Model results show that most equatorial PADs of 1-10s of keV electrons in Earth's inner magnetosphere are pancake PADs, and the lack of butterfly PADs is likely due to their relatively flat or positive flux radial gradients at higher altitudes. During geomagnetically quiet times, more anisotropic distributions of 1-10s of keV electrons at dayside than nightside are observed, which could be responsible for moderate chorus wave activities at dayside during quiet times as reported by previous studies. During active times, the anisotropy of 1-10s of keV electrons significantly enhances, consistent with the enhanced chorus wave activity during active times and suggesting the critical role of 1-10s of keV electrons in generating chorus waves in Earth's inner magnetosphere. Different enhanced anisotropy patterns of different energy electrons are also observed during active times: at R > ~4 RE, keV electrons are more anisotropic at dawn to noon, while 10s of keV electrons have larger anisotropy at midnight to dawn. These differences, combined with the statistical distribution of chorus waves shown in previous studies, suggest the differential roles of electrons with different energies in generating chorus waves with different properties. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1029/2020JA028322 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 20 StartPage: 1 Subjects: – SubjectFull: Van Allen radiation belts Type: general – SubjectFull: Magnetosphere Type: general – SubjectFull: Solar magnetism Type: general – SubjectFull: Interplanetary medium Type: general – SubjectFull: Interplanetary magnetic fields Type: general Titles: – TitleFull: Equatorial Pitch Angle Distributions of 1-50 keV Electrons in Earth's Inner Magnetosphere: An Empirical Model Based on the Van Allen Probes Observations. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Zhao, H. – PersonEntity: Name: NameFull: Friedel, R. H. W. – PersonEntity: Name: NameFull: Chen, Y. – PersonEntity: Name: NameFull: Baker, D. N. – PersonEntity: Name: NameFull: Li, X. – PersonEntity: Name: NameFull: Malaspina, D. M. – PersonEntity: Name: NameFull: Larsen, B. A. – PersonEntity: Name: NameFull: Skoug, R. M. – PersonEntity: Name: NameFull: Funsten, H. O. – PersonEntity: Name: NameFull: Reeves, G. D. – PersonEntity: Name: NameFull: Boyd, A. J. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 01 Text: Jan2021 Type: published Y: 2021 Identifiers: – Type: issn-print Value: 21699380 Numbering: – Type: volume Value: 126 – Type: issue Value: 1 Titles: – TitleFull: Journal of Geophysical Research. Space Physics Type: main |
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