On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration
Observations of the electron radiation belts have shown links between increases in the low-energy seed population and enhancements in the >1-MeV flux. During active times, low-energy electrons are introduced to the radiation belt region before being accelerated to higher energies via a range of m...
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American Geophysical Union
2019
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ftnerc:oai:nora.nerc.ac.uk:522052 2023-05-15T13:41:42+02:00 On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration Allison, Hayley Horne, Richard Glauert, Sarah Del Zanna, Guilio 2019-05-17 text http://nora.nerc.ac.uk/id/eprint/522052/ https://nora.nerc.ac.uk/id/eprint/522052/1/Allison_et_al-2019-Journal_of_Geophysical_Research__Space_Physics.pdf en eng American Geophysical Union https://nora.nerc.ac.uk/id/eprint/522052/1/Allison_et_al-2019-Journal_of_Geophysical_Research__Space_Physics.pdf Allison, Hayley orcid:0000-0002-6665-2023 Horne, Richard orcid:0000-0002-0412-6407 Glauert, Sarah orcid:0000-0003-0149-8608 Del Zanna, Guilio. 2019 On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration. Journal of Geophysical Research: Space Physics, 124 (4). 2628-2642. https://doi.org/10.1029/2019JA026516 <https://doi.org/10.1029/2019JA026516> Publication - Article NonPeerReviewed 2019 ftnerc https://doi.org/10.1029/2019JA026516 2023-02-04T19:47:38Z Observations of the electron radiation belts have shown links between increases in the low-energy seed population and enhancements in the >1-MeV flux. During active times, low-energy electrons are introduced to the radiation belt region before being accelerated to higher energies via a range of mechanisms. The impact of variations in the seed population on the 1-MeV flux level were explored using the British Antarctic Survey Radiation Belt Model. We find that, for a period from the 21 April to 9 May 2013, the increase in the low-energy electron flux was vital to recreate the observed 1-MeV flux enhancement on the 1 May but was less important for the 1-MeV enhancement on the 27 April 2013. To better understand the relationships between the different energy populations, a series of idealized experiments with the 2-D British Antarctic Survey Radiation Belt Model were performed, which highlight a careful balance between losses and acceleration from chorus waves. Seed population enhancements alter this balance by increasing the phase space density gradient, and consequently, the rate of energy diffusion, allowing acceleration to surpass loss. Additionally, we demonstrate that even with the same chorus diffusion coefficients and the same low-energy boundary condition, the flux of ∼500-keV to 1-MeV electrons increased when starting with a hard spectrum but decreased for a soft initial spectrum. This suggests that initial energy gradients in the phase space density were important to determine whether >500-keV electrons were enhanced due to chorus wave acceleration Article in Journal/Newspaper Antarc* Antarctic British Antarctic Survey Natural Environment Research Council: NERC Open Research Archive Antarctic Journal of Geophysical Research: Space Physics |
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Open Polar |
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Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
English |
description |
Observations of the electron radiation belts have shown links between increases in the low-energy seed population and enhancements in the >1-MeV flux. During active times, low-energy electrons are introduced to the radiation belt region before being accelerated to higher energies via a range of mechanisms. The impact of variations in the seed population on the 1-MeV flux level were explored using the British Antarctic Survey Radiation Belt Model. We find that, for a period from the 21 April to 9 May 2013, the increase in the low-energy electron flux was vital to recreate the observed 1-MeV flux enhancement on the 1 May but was less important for the 1-MeV enhancement on the 27 April 2013. To better understand the relationships between the different energy populations, a series of idealized experiments with the 2-D British Antarctic Survey Radiation Belt Model were performed, which highlight a careful balance between losses and acceleration from chorus waves. Seed population enhancements alter this balance by increasing the phase space density gradient, and consequently, the rate of energy diffusion, allowing acceleration to surpass loss. Additionally, we demonstrate that even with the same chorus diffusion coefficients and the same low-energy boundary condition, the flux of ∼500-keV to 1-MeV electrons increased when starting with a hard spectrum but decreased for a soft initial spectrum. This suggests that initial energy gradients in the phase space density were important to determine whether >500-keV electrons were enhanced due to chorus wave acceleration |
format |
Article in Journal/Newspaper |
author |
Allison, Hayley Horne, Richard Glauert, Sarah Del Zanna, Guilio |
spellingShingle |
Allison, Hayley Horne, Richard Glauert, Sarah Del Zanna, Guilio On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration |
author_facet |
Allison, Hayley Horne, Richard Glauert, Sarah Del Zanna, Guilio |
author_sort |
Allison, Hayley |
title |
On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration |
title_short |
On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration |
title_full |
On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration |
title_fullStr |
On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration |
title_full_unstemmed |
On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration |
title_sort |
on the importance of gradients in the low energy electron phase space density for relativistic electron acceleration |
publisher |
American Geophysical Union |
publishDate |
2019 |
url |
http://nora.nerc.ac.uk/id/eprint/522052/ https://nora.nerc.ac.uk/id/eprint/522052/1/Allison_et_al-2019-Journal_of_Geophysical_Research__Space_Physics.pdf |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic British Antarctic Survey |
genre_facet |
Antarc* Antarctic British Antarctic Survey |
op_relation |
https://nora.nerc.ac.uk/id/eprint/522052/1/Allison_et_al-2019-Journal_of_Geophysical_Research__Space_Physics.pdf Allison, Hayley orcid:0000-0002-6665-2023 Horne, Richard orcid:0000-0002-0412-6407 Glauert, Sarah orcid:0000-0003-0149-8608 Del Zanna, Guilio. 2019 On the importance of gradients in the low energy electron phase space density for relativistic electron acceleration. Journal of Geophysical Research: Space Physics, 124 (4). 2628-2642. https://doi.org/10.1029/2019JA026516 <https://doi.org/10.1029/2019JA026516> |
op_doi |
https://doi.org/10.1029/2019JA026516 |
container_title |
Journal of Geophysical Research: Space Physics |
_version_ |
1766154288555360256 |