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Wave acceleration of electrons in the Van Allen radiation belts

Abstract

The Van Allen radiation belts1 are two regions encircling the Earth in which energetic charged particles are trapped inside the Earth's magnetic field. Their properties vary according to solar activity2,3 and they represent a hazard to satellites and humans in space4,5. An important challenge has been to explain how the charged particles within these belts are accelerated to very high energies of several million electron volts. Here we show, on the basis of the analysis of a rare event where the outer radiation belt was depleted and then re-formed closer to the Earth6, that the long established theory of acceleration by radial diffusion is inadequate; the electrons are accelerated more effectively by electromagnetic waves at frequencies of a few kilohertz. Wave acceleration can increase the electron flux by more than three orders of magnitude over the observed timescale of one to two days, more than sufficient to explain the new radiation belt. Wave acceleration could also be important for Jupiter, Saturn and other astrophysical objects with magnetic fields.

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Figure 1: Satellite and ground based data during the Hallowe'en storm.
Figure 2: Waves observed at Palmer station, Antarctica, on 1 November 2003.
Figure 3: Waves observed by the Cluster spacecraft.
Figure 4: Simulation results.

References

  1. Van Allen, J. A. in Discovery of the Magnetosphere (eds Gillmor, C. S. & Spreiter, J. R.) 235–251 (Vol. 7, History of Geophysics, American Geophysical Union, Washington DC, 1997)

    Book  Google Scholar 

  2. Baker, D. N., Blake, J. B., Klebesadel, R. W. & Higbie, P. R. Highly relativistic electrons in the Earth's outer magnetosphere 1. Lifetimes and temporal history 1979–1984. J. Geophys. Res. 91, 4265–4276 (1986)

    ADS  Article  Google Scholar 

  3. Li, X., Baker, D. N., Kanekal, S. G., Looper, M. & Temerin, M. Long term measurements of radiation belts by SAMPEX and their variations. Geophys. Res. Lett. 28, 3827–3830 (2001)

    ADS  Article  Google Scholar 

  4. Baker, D. N., Allen, J. H., Kanekal, S. G. & Reeves, G. D. Disturbed space environment may have been related to pager satellite failure. Eos 79, 477 (1998)

    ADS  Article  Google Scholar 

  5. Webb, D. F. & Allen, J. H. Spacecraft and ground anomalies related to the October-November 2003 solar activity. Space Weath. 2, doi:10.1029/2004SW000075 (2004)

  6. Baker, D. N. et al. An extreme distortion of the Van Allen belt arising from the Hallowe'en solar storm in 2003. Nature 432, 878–881 (2004)

    ADS  CAS  Article  Google Scholar 

  7. Falthammar, C.-G. Effects of time dependent electric fields on geomagnetically trapped radiation. J. Geophys. Res. 70, 2503–2516 (1965)

    ADS  MathSciNet  Article  Google Scholar 

  8. Schulz, M. & Lanzerotti, L. J. Particle Diffusion in the Radiation Belts (Springer, New York, 1974)

    Book  Google Scholar 

  9. Elkington, S. R., Hudson, M. K. & Chan, A. A. Acceleration of relativistic electrons via drift resonant interactions with toroidal-mode Pc-5 ULF oscillations. Geophys. Res. Lett. 26, 3273–3276 (1999)

    ADS  Article  Google Scholar 

  10. Summers, D., Thorne, R. M. & Xiao, F. Relativistic theory of wave-particle resonant diffusion with application to electron acceleration in the magnetosphere. J. Geophys. Res. 103, 20487–20500 (1998)

    ADS  CAS  Article  Google Scholar 

  11. Horne, R. B. & Thorne, R. M. Potential waves for relativistic electron scattering and stochastic acceleration during magnetic storms. Geophys. Res. Lett. 25, 3011–3014 (1998)

    ADS  Article  Google Scholar 

  12. Tsurutani, B. T. & Smith, E. J. Postmidnight chorus: A substorm phenomenon. J. Geophys. Res. 79, 118–127 (1974)

    ADS  Article  Google Scholar 

  13. Brautigam, D. H. & Albert, J. M. Radial diffusion analysis of outer radiation belt electrons during the October 9, 1990, magnetic storm. J. Geophys. Res. 105, 291–309 (2000)

    ADS  Article  Google Scholar 

  14. Shprits, Y. Y. & Thorne, R. M. Time dependent radial diffusion modeling of relativistic electrons with realistic loss rates. Geophys. Res. Lett. 31, doi:10.1029/2004GL019591 (2004)

  15. Kennel, C. F. & Petschek, H. E. Limit on stably trapped particle fluxes. J. Geophys. Res. 71, 1–28 (1966)

    ADS  Article  Google Scholar 

  16. Helliwell, R. A. A theory of discreet emissions from the magnetosphere. J. Geophys. Res. 72, 4773–4790 (1967)

    ADS  Article  Google Scholar 

  17. Horne, R. B., Glauert, S. A. & Thorne, R. M. Resonant diffusion of radiation belt electrons by whistler-mode chorus. Geophys. Res. Lett. 30, doi:10.1029/2003GL016963 (2003)

  18. Sheeley, B. W., Moldwin, M. B., Rassoul, H. K. & Anderson, R. R. An empirical plasmasphere and trough density model: CRRES observations. J. Geophys. Res. 106, 25631–25641 (2001)

    ADS  Article  Google Scholar 

  19. Meredith, N. P., Horne, R. B., Thorne, R. M. & Anderson, R. R. Favoured regions for chorus-driven electron acceleration to relativistic energies in the Earth's outer radiation belt. Geophys. Res. Lett. 30, 1871, doi:10.1029/2003GL017698 (2003)

    ADS  Google Scholar 

  20. Horne, R. B. et al. Timescale for radiation belt electron acceleration by whistler mode chorus waves. J. Geophys. Res. 110, A03225, doi:10.1029/2004JA010811 (2005)

    ADS  Article  Google Scholar 

  21. Glauert, S. A. & Horne, R. B. Calculation of pitch angle and energy diffusion coefficients with the PADIE code. J. Geophys. Res. 110, A04206, doi:10.1029/2004JA010851 (2005)

    ADS  Article  Google Scholar 

  22. Lyons, L. R. & Thorne, R. M. Equilibrium structure of radiation belt electrons. J. Geophys. Res. 78, 2142–2149 (1973)

    ADS  Article  Google Scholar 

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Acknowledgements

We thank E. Lucek for providing fluxgate magnetometer data from the Cluster spacecraft, and N. Cornilleau-Wehrlin for an independent assessment of the wave magnetic power spectral density. This work was supported in part by the UK Natural Environment Research Council (NERC), the NSF and NASA.

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Correspondence to Richard B. Horne.

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Supplementary information

Supplementary Table S1

A table of diffusion coefficients used in the simulation model. (DOC 27 kb)

Supplementary Data

Details of the wave model used to calculate the diffusion rates presented in Supplementary Table S1. (DOC 19 kb)

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Horne, R., Thorne, R., Shprits, Y. et al. Wave acceleration of electrons in the Van Allen radiation belts. Nature 437, 227–230 (2005). https://doi.org/10.1038/nature03939

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