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Global morphology of chorus waves in the outer radiation belt and the effect of geomagnetic activity and fpe/fce

Whistler-mode chorus waves play a key role in driving radiation belt dynamics by enabling both acceleration of electrons to relativistic energies as well as their loss into the atmosphere via pitch-angle scattering. The ratio between the electron plasma frequency (fpe) and the electron gyrofrequency (fce) significantly influences the efficiency of these processes, with electron acceleration being most effective during periods of low fpe/fce. In this study, a combined total of approximately 24.5 years of THEMIS wave data are analyzed to show how chorus wave intensity and spatial location vary with relative frequency, geomagnetic activity and fpe/fce. Results demonstrate that the strongest chorus emissions are observed during active conditions. At these times, equatorial chorus at low relative frequencies (flhr<f<0.1fce) is strongest when fpe/fce is high (fpe/fce>10) primarily in the region 5<L*<8, from 22:00-12:00 MLT. In sharp contrast at high relative frequencies (0.5fce<f<0.7fce), the equatorial chorus is strongest when fpe/fce is low (fpefce<6) mainly in the region 4<L*<6 from 21:00-09:00 MLT. At intermediate relative frequencies (0.3fce<f<0.4fce), equatorial chorus is strongest in the region 3.5<L*<8 from 21:00-12:00 MLT. In the off-equatorial region the strongest waves are seen in the frequency range (0.1fce<f<0.3fce) between 5<L*<8 and 06:00-15:00 MLT and again are mostly independent of fpe/fce. We show that the location of the strongest waves can be largely explained in terms of the source electrons being in the required energy range for resonance and the absence of Landau damping and highlight the regions where electron acceleration to relativistic energies is likely to be mostly significant.

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Date (Creation)
2026-01-09
Date (Revision)
2026-01-09
Date (Publication)
2026-01-09
Date (released)
2026-01-09
Edition
1.0
Unique resource identifier
https://doi.org/10.5285/5586a319-fa57-4bb6-af3a-3746cd643c0d
Codespace
doi
Unique resource identifier
GB/NERC/BAS/PDC/02134
Codespace
https://data.bas.ac.uk/
Other citation details
Please cite this item as: Bunting, K., Meredith, N., Bortnik, J., Ma, Q., Matsuura, R., & Shen, X. (2026). Global morphology of chorus waves in the outer radiation belt and the effect of geomagnetic activity and fpe/fce (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/5586a319-fa57-4bb6-af3a-3746cd643c0d
Credit
No credit.
Status
completed Completed
Author
  British Antarctic Survey - Bunting, Kaine ( Researcher )
Author
  British Antarctic Survey - Meredith, Nigel ( Researcher )
Author
  UCLA Space institute - Bortnik, Jacob ( Researcher )
Author
  UCLA - Ma, Qianli ( Researcher )
Author
  UCLA - Matsuura, Ryoma ( Researcher )
Author
  Boston University - Shen, Xiao-Chen ( Researcher )
Point of contact
  NERC EDS UK Polar Data Centre
British Antarctic Survey, High Cross, Madingley Road , Cambridge , Cambridgeshire , CB3 0ET , United Kingdom
+44 (0)1223 221400
https://www.bas.ac.uk/team/business-teams/information-services/uk-polar-data-centre/
Maintenance and update frequency
asNeeded As needed
Maintenance note
completed Completed
Global Change Master Directory (GCMD) Science Keywords
  • EARTH SCIENCE > Sun-earth Interactions > Ionosphere/Magnetosphere Dynamics > Plasma Waves
  • EARTH SCIENCE > Sun-earth Interactions > Solar Energetic Particle Properties
Theme
  • Radiation belts
  • Wave-particle interaction
  • Whistler-mode chorus
Place
  • Global
GEMET - INSPIRE themes, version 1.0
  • Atmospheric conditions
Access constraints
otherRestrictions Other restrictions
Other constraints
no limitations to public access
Access constraints
otherRestrictions Other restrictions
Other constraints
no limitations
Use constraints
license License
Other constraints
This dataset is supplied under the Open Government Licence v3.0: https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/
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url
Codespace
url
Association Type
crossReference Cross reference
Spatial representation type
textTable Text, table
Metadata language
engEnglish
Character set
utf8 UTF8
Topic category
  • Geoscientific information
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Supplemental Information
It is recommended that careful attention be paid to the contents of any data, and that the author be contacted with any questions regarding appropriate use. If you find any errors or omissions, please report them to polardatacentre@bas.ac.uk.
Date (Publication)
2008-11-12
Publisher
  European Petroleum Survey Group
https://www.epsg-registry.org/
Unique resource identifier
urn:ogc:def:crs:EPSG::3031
Version
6.18.3

Distributor

Distributor
  NERC EDS UK Polar Data Centre
British Antarctic Survey, High Cross, Madingley Road , Cambridge , Cambridgeshire , CB3 0ET , United Kingdom
+44 (0)1223 221400
https://www.bas.ac.uk/team/business-teams/information-services/uk-polar-data-centre/
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dataset Dataset
Statement

Methodology:

The data used in this study were collected by the NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. Specifically, we primarily use magnetic (fff) wave data. This data is publicly available at http://themis.ssl.berkeley edu/data/themis. Full details of the subsequent analysis are given in Bunting et al. (2025)

Data collection:

THEMIS data is used from the THEMIS -A, -D and -E satellites. THEMIS high resolution (fff) data is the fast Fourier transform of magnetic variations observed by the search coil magnetometer on board. The Fluxgate magnetometer gives the background magnetic field strength.

Data quality:

THEMIS data have been calibrated and quality-controlled prior to release.

File identifier
5586a319-fa57-4bb6-af3a-3746cd643c0d XML
Metadata language
engEnglish
Character set
utf8 UTF8
Hierarchy level
dataset Dataset
Hierarchy level name
dataset
Date stamp
2026-01-09
Metadata standard name
ISO 19115 Geographic Information - Metadata
Metadata standard version
ISO 19115:2003(E)
Point of contact
  NERC EDS UK Polar Data Centre
British Antarctic Survey, High Cross, Madingley Road , Cambridge , Cambridgeshire , CB3 0ET , United Kingdom
+44 (0)1223 221400
https://www.bas.ac.uk/team/business-teams/information-services/uk-polar-data-centre/
 
 

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Keywords

Radiation belts Wave-particle interaction Whistler-mode chorus
GEMET - INSPIRE themes, version 1.0
Atmospheric conditions
Global Change Master Directory (GCMD) Science Keywords
EARTH SCIENCE > Sun-earth Interactions > Ionosphere/Magnetosphere Dynamics > Plasma Waves EARTH SCIENCE > Sun-earth Interactions > Solar Energetic Particle Properties

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