Statistical investigation on equatorial pitch angle distribution of energetic electrons in Earth’s outer radiation belt during CME- and CIR-driven storms
We present a statistical investigation (September 2012 - September 2017) of pitch angle distribution (PAD) of energetic electrons (∼30 keV - 1 MeV) in the outer radiation belt (L ≥ 3) during CME- and CIR-driven geomagnetic storms using Van Allen Probe measurements. We selected geomagnetic storms bas...
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Frontiers Media S.A.
2022-08-01
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fspas.2022.986061/full |
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| author | S. Chakraborty S. Chakraborty D. Chakrabarty G. D. Reeves D. N. Baker I. J. Rae |
| author_facet | S. Chakraborty S. Chakraborty D. Chakrabarty G. D. Reeves D. N. Baker I. J. Rae |
| author_sort | S. Chakraborty |
| collection | DOAJ |
| description | We present a statistical investigation (September 2012 - September 2017) of pitch angle distribution (PAD) of energetic electrons (∼30 keV - 1 MeV) in the outer radiation belt (L ≥ 3) during CME- and CIR-driven geomagnetic storms using Van Allen Probe measurements. We selected geomagnetic storms based on minimum of SYM-H being less than -50 nT and classified the storms according to their drivers. Thus, we obtained 23 CME- and 24 CIR-driven storms. During the storm intervals, pitch angle resolved electron flux measurements are obtained from the MagEIS instrument on-board Van Allen Probe-A spacecraft. We assume symmetric pitch angle distributions around 90° pitch angle and fit the observed PADs with Legendre polynomials after propagating them to the magnetic equator. Legendre coefficients c2 and c4, and the ratio R = |c2/c4| are used to categorize the different PAD types. To resolve the spatio-temporal distribution of PADs, these coefficients are binned in 5 L-shell bins, 12 MLT bins for seven energy channels and four storm phases. We found that several hundreds of keV electrons exhibit clear dependence on local time, storm phases and storm drivers, with increased anisotropy for CME-driven storms during main and early recovery phases. On the contrary, we found that tens of keV electrons do not exhibit significant dependence on these parameters. We have discussed the different physical mechanisms responsible for the observed MLT dependent PADs and found drift-shell splitting to be the major contributor. |
| first_indexed | 2024-12-10T18:11:07Z |
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| id | doaj.art-c53dd67e5d174c3fbadf4bf99d63ed94 |
| institution | Directory Open Access Journal |
| issn | 2296-987X |
| language | English |
| last_indexed | 2024-12-10T18:11:07Z |
| publishDate | 2022-08-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Astronomy and Space Sciences |
| spelling | doaj.art-c53dd67e5d174c3fbadf4bf99d63ed942022-12-22T01:38:26ZengFrontiers Media S.A.Frontiers in Astronomy and Space Sciences2296-987X2022-08-01910.3389/fspas.2022.986061986061Statistical investigation on equatorial pitch angle distribution of energetic electrons in Earth’s outer radiation belt during CME- and CIR-driven stormsS. Chakraborty0S. Chakraborty1D. Chakrabarty2G. D. Reeves3D. N. Baker4I. J. Rae5Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle-upon-Tyne, United KingdomSpace and Atmospheric Sciences Division, Physical Research Laboratory, Ahmedabad, IndiaSpace and Atmospheric Sciences Division, Physical Research Laboratory, Ahmedabad, IndiaSpace Science and Applications Group, Los Alamos National Laboratory, Los Alamos, NM, United StatesLaboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, United StatesDepartment of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle-upon-Tyne, United KingdomWe present a statistical investigation (September 2012 - September 2017) of pitch angle distribution (PAD) of energetic electrons (∼30 keV - 1 MeV) in the outer radiation belt (L ≥ 3) during CME- and CIR-driven geomagnetic storms using Van Allen Probe measurements. We selected geomagnetic storms based on minimum of SYM-H being less than -50 nT and classified the storms according to their drivers. Thus, we obtained 23 CME- and 24 CIR-driven storms. During the storm intervals, pitch angle resolved electron flux measurements are obtained from the MagEIS instrument on-board Van Allen Probe-A spacecraft. We assume symmetric pitch angle distributions around 90° pitch angle and fit the observed PADs with Legendre polynomials after propagating them to the magnetic equator. Legendre coefficients c2 and c4, and the ratio R = |c2/c4| are used to categorize the different PAD types. To resolve the spatio-temporal distribution of PADs, these coefficients are binned in 5 L-shell bins, 12 MLT bins for seven energy channels and four storm phases. We found that several hundreds of keV electrons exhibit clear dependence on local time, storm phases and storm drivers, with increased anisotropy for CME-driven storms during main and early recovery phases. On the contrary, we found that tens of keV electrons do not exhibit significant dependence on these parameters. We have discussed the different physical mechanisms responsible for the observed MLT dependent PADs and found drift-shell splitting to be the major contributor.https://www.frontiersin.org/articles/10.3389/fspas.2022.986061/fullpitch angle distributionouter radiation beltenergetic electronsvan allen probesgeomagnetic stormsCME |
| spellingShingle | S. Chakraborty S. Chakraborty D. Chakrabarty G. D. Reeves D. N. Baker I. J. Rae Statistical investigation on equatorial pitch angle distribution of energetic electrons in Earth’s outer radiation belt during CME- and CIR-driven storms Frontiers in Astronomy and Space Sciences pitch angle distribution outer radiation belt energetic electrons van allen probes geomagnetic storms CME |
| title | Statistical investigation on equatorial pitch angle distribution of energetic electrons in Earth’s outer radiation belt during CME- and CIR-driven storms |
| title_full | Statistical investigation on equatorial pitch angle distribution of energetic electrons in Earth’s outer radiation belt during CME- and CIR-driven storms |
| title_fullStr | Statistical investigation on equatorial pitch angle distribution of energetic electrons in Earth’s outer radiation belt during CME- and CIR-driven storms |
| title_full_unstemmed | Statistical investigation on equatorial pitch angle distribution of energetic electrons in Earth’s outer radiation belt during CME- and CIR-driven storms |
| title_short | Statistical investigation on equatorial pitch angle distribution of energetic electrons in Earth’s outer radiation belt during CME- and CIR-driven storms |
| title_sort | statistical investigation on equatorial pitch angle distribution of energetic electrons in earth s outer radiation belt during cme and cir driven storms |
| topic | pitch angle distribution outer radiation belt energetic electrons van allen probes geomagnetic storms CME |
| url | https://www.frontiersin.org/articles/10.3389/fspas.2022.986061/full |
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