Radial diffusion simulations of the 20 September 2007 radiation belt dropout
This is a study of a dropout of radiation belt electrons, associated with an isolated solar wind density pulse on 20 September 2007, as seen by the solid-state telescopes (SST) detectors on THEMIS (Time History of Events and Macroscale Interactions during Substorms). Omnidirectional fluxes were...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2014-08-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/32/925/2014/angeo-32-925-2014.pdf |
| _version_ | 1818953702157844480 |
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| author | J. Albert |
| author_facet | J. Albert |
| author_sort | J. Albert |
| collection | DOAJ |
| description | This is a study of a dropout of radiation belt electrons, associated with an
isolated solar wind density pulse on 20 September 2007, as seen by the solid-state
telescopes (SST)
detectors on THEMIS (Time History of Events and Macroscale
Interactions during Substorms). Omnidirectional fluxes were converted to phase space
density at constant invariants <i>M</i> = 700 MeV G<sup>−1</sup> and <i>K</i> = 0.014 <i>R</i><sub>E</sub> G<sup>1/2</sup>, with the assumption of
local pitch angle α ≈ 80° and using the T04 magnetic field
model. The last closed drift shell, which was calculated throughout the time
interval, never came within the simulation outer boundary of <i>L</i><sup>*</sup> = 6. It is
found, using several different models for diffusion rates, that radial
diffusion alone only allows the data-driven, time-dependent boundary values
at <i>L</i><sub>max</sub> = 6 and <i>L</i><sub>min</sub> = 3.7 to propagate a few tenths of an <i>R</i><sub>E</sub> during
the simulation; far too slow to account for the dropout observed over the
broad range of <i>L</i><sup>*</sup> = 4–5.5. Pitch angle diffusion via resonant
interactions with several types of waves (chorus, electromagnetic ion
cyclotron waves, and plasmaspheric and plume hiss) also seems problematic,
for several reasons which are discussed. |
| first_indexed | 2024-12-20T10:10:28Z |
| format | Article |
| id | doaj.art-961c6fce0f9248c7b649e22be877228f |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-20T10:10:28Z |
| publishDate | 2014-08-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-961c6fce0f9248c7b649e22be877228f2022-12-21T19:44:10ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762014-08-013292593410.5194/angeo-32-925-2014Radial diffusion simulations of the 20 September 2007 radiation belt dropoutJ. Albert0Air Force Research Laboratory, 3550 Aberdeen Avenue SE, Kirtland AFB, NM, USAThis is a study of a dropout of radiation belt electrons, associated with an isolated solar wind density pulse on 20 September 2007, as seen by the solid-state telescopes (SST) detectors on THEMIS (Time History of Events and Macroscale Interactions during Substorms). Omnidirectional fluxes were converted to phase space density at constant invariants <i>M</i> = 700 MeV G<sup>−1</sup> and <i>K</i> = 0.014 <i>R</i><sub>E</sub> G<sup>1/2</sup>, with the assumption of local pitch angle α ≈ 80° and using the T04 magnetic field model. The last closed drift shell, which was calculated throughout the time interval, never came within the simulation outer boundary of <i>L</i><sup>*</sup> = 6. It is found, using several different models for diffusion rates, that radial diffusion alone only allows the data-driven, time-dependent boundary values at <i>L</i><sub>max</sub> = 6 and <i>L</i><sub>min</sub> = 3.7 to propagate a few tenths of an <i>R</i><sub>E</sub> during the simulation; far too slow to account for the dropout observed over the broad range of <i>L</i><sup>*</sup> = 4–5.5. Pitch angle diffusion via resonant interactions with several types of waves (chorus, electromagnetic ion cyclotron waves, and plasmaspheric and plume hiss) also seems problematic, for several reasons which are discussed.https://www.ann-geophys.net/32/925/2014/angeo-32-925-2014.pdf |
| spellingShingle | J. Albert Radial diffusion simulations of the 20 September 2007 radiation belt dropout Annales Geophysicae |
| title | Radial diffusion simulations of the 20 September 2007 radiation belt dropout |
| title_full | Radial diffusion simulations of the 20 September 2007 radiation belt dropout |
| title_fullStr | Radial diffusion simulations of the 20 September 2007 radiation belt dropout |
| title_full_unstemmed | Radial diffusion simulations of the 20 September 2007 radiation belt dropout |
| title_short | Radial diffusion simulations of the 20 September 2007 radiation belt dropout |
| title_sort | radial diffusion simulations of the 20 september 2007 radiation belt dropout |
| url | https://www.ann-geophys.net/32/925/2014/angeo-32-925-2014.pdf |
| work_keys_str_mv | AT jalbert radialdiffusionsimulationsofthe20september2007radiationbeltdropout |