Chakraborty, Suman, Mann, Ian, Watt, Clare, Rae, Jonathan, Olifer, L., Ozeke, L. G., Sandhu, Jasmine, Mauk, B. H. and Spence, H. (2022) Intense chorus waves are the cause of flux-limiting in the heart of the outer radiation belt. Scientific Reports, 12 (1). p. 21717. ISSN 2045-2322
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Abstract
Chorus waves play a key role in outer Van Allen electron belt dynamics through cyclotron resonance. Here, we use Van Allen Probes data to reveal a new and distinct population of intense chorus waves excited in the heart of the radiation belt during the main phase of geomagnetic storms. The power of the waves is typically ~ 2–3 orders of magnitude greater than pre-storm levels, and are generated when fluxes of ~ 10–100 keV electrons approach or exceed the Kennel–Petschek limit. These intense chorus waves rapidly scatter electrons into the loss cone, capping the electron flux to a value close to the limit predicted by Kennel and Petschek over 50 years ago. Our results are crucial for understanding the limits to radiation belt fluxes, with accurate models likely requiring the inclusion of this chorus wave-driven flux-limiting process, that is independent of the acceleration mechanism or source responsible for enhancing the flux.
| Item Type: | Article |
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| Additional Information: | Funding information: The interplanetary parameters and geomagnetic indices are obtained from the website (https:// cdaweb. gsfc. nasa.gov/ cgi- bin/eval2.cgi). The Van Allen Probe data used in this study are available at the websites (http:// emfis is.physi cs. uiowa. edu/ Flight/ for EMFISIS, and http:// www. rbsp- ect. lanl. gov/ data_ pub/ for ECT. The POES data used in this study can be found at https:// www. ngdc. noaa. gov/ stp/ satel lite/ poes/ dataa ccess. html. The authors thank all of the MagEIS and EMFISIS teams of the Van Allen Probe, and the POES team for the data. SC is supported by STFC Grant ST/V006320/1 and NERC Grants NE/V002554/2 and NE/P017185/2. IRM is supported by a Royal Society Wolfson Visiting Fellowship. IRM is also supported by the Canadian Space Agency (CSA), by Canadian NSERC, and a DND/NSERC Discovery Grant Supplement. CEJW is supported in part by STFC Grant ST/W000369/1, and NERC Grant NE/V0002759/2. IJR is supported in part by STFC Grant ST/V006320/1 and NERC Grants NE/V002554/2 and NE/P017185/2. JKS acknowledges support from NERC Grants NE/P017185/2, NE/V002554/2 and STFC 376 Grant ST/V006320/1. |
| Subjects: | F300 Physics F500 Astronomy |
| Department: | Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering |
| Depositing User: | John Coen |
| Date Deposited: | 16 Dec 2022 14:26 |
| Last Modified: | 19 Dec 2022 10:45 |
| URI: | https://nrl.northumbria.ac.uk/id/eprint/50916 |
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