Skip to main content

Main-phase creation of “seed” electrons in the outer radiation belt


During a geomagnetic storm in early November 1993, NOAA satellite observations revealed that a population of energetic electrons appeared in the center of the outer radiation belt during the main phase of the storm. At the beginning of the main phase of the magnetic storm, the number of electrons with energies from 30 keV to 100 keV increased rapidly and contributed to build up of the ring current. At the end of the main phase the flux of electrons with energies greater than 300 keV increased significantly. Akebono satellite observations showed that the flux of electrons with energies ranging from 300 keV to 950 keV increased late of the storm main phase and that the flux of electrons with energies from 950 keV to 2.5 MeV increased during the storm recovery phase. The electron flux increase observed by both NOAA and Akebono took place first in the central part of the outer radiation belt (L~4) and propagated to higher L shells with a significant time delay. We think that the ring current electrons that appeared first and near L~4 during the main phase seeded the subsequent increase in the flux of MeV electrons in the entire outer radiation belt.


  • Baker, D. N., J. H. Allen, S. G. Kenekal, and G. D. Reeves, Disturbed space environment may have been related to pager satellite failure, EOS, 79, 477–483, 1998.

    Article  Google Scholar 

  • Freeman, J. W., T. P. O’Brien, A. A. Chan, and R. A. Wolf, Energetic electrons at geostationary orbit during the November 3–4, 1993 storm: Spatial/temporal morphology, characterization by a power law spectrum and representation by an artificial network, J. Geophys. Res., 103, 26251–26260, 1998.

    Article  Google Scholar 

  • Knipp, D. J. et al., An overview of the early November 1993 geomagnetic storm, J. Geophys. Res., 103, 26197–26220, 1998.

    Google Scholar 

  • Kozyra, J. U., V. K. Jordanova, J. E. Borovsky, M. F. Thomsen, D. J. Knipp, D. S. Evans, D. J. McComas, and T. E. Cayton, Effects of a high-density sheet on ring current development during the November 2–6, 1993, magnetic storm, J. Geophys. Res., 103, 26285–26305, 1

    Article  Google Scholar 

  • Li, X., D. N. Baker, M. Temerin, T. E. Cayton, G. D. Reeves, R. A. Christensen, J. B. Blake, M. D. Looper, R. Nakamura, and S. G. Kenekal, Observations of the outer zone electron variation during the November 3–4, 1993, magnetic storm, J. Geophys. Res., 102, 14123–14140, 1997.

    Article  Google Scholar 

  • Mitsui, C., A. Tsutai, T. Nagai, T. Kohno, and F. Makino, Energetic electron filling of the slot region: EXOS-D observations, Earth Planets Space, 1999 (submitted).

  • McIlwain, C. E., Ring current effects on trapped particles, J. Geophys. Res., 71, 3623–3628, 1966.

    Article  Google Scholar 

  • Nakamura, R., K. Kamei, and Y. Kamide, SAMPEX observation of storm-associated electron flux variation in the outer radiation belt, J. Geophys. Res., 103, 26261–26269, 1998.

    Article  Google Scholar 

  • Obara, T., M. Den, T. Nagatsuma, and E. Sagawa, Enhancement of the trapped radiation electrons at 6.6 Re during the storm recovery phase—results from GMS/SEM observation—, Proceeding on NIPR Symposium on Upper Atmospheric Phys., 12, 86–93, 1998.

    Google Scholar 

  • Raben, V. J., D. E. Evans, H. H. Sauer, S. R. Sahm, and M. Huynh, TIROS/NOAA satellite space environment monitor data archive documentation: 1995 update, NOAA Tech. Memo. ERL SEL-86, 1995.

  • Yokoyama, N. and Y. Kamide, Statistical nature of geomagnetic storms, J. Geophys. Res., 102, 14215–14222, 1997.

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to T. Obara.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Obara, T., Nagatsuma, T., Den, M. et al. Main-phase creation of “seed” electrons in the outer radiation belt. Earth Planet Sp 52, 41–47 (2000).

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


  • Solar Wind
  • Magnetic Storm
  • Geomagnetic Storm
  • Relativistic Electron
  • Electron Flux