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Seasonal polar cap radiation zones in dayside magnetosphere


The phenomenon of quasi-stable trapping of charged particles in the keV to MeV energy range within the polar cusp region of the Earth’s magnetosphere is explored. The remote equatorial magnetic field lines on the dayside magnetosphere are compressed by the solar wind and exhibit two local minima in the geomagnetic field strength along the field line in high latitudes. These minima, on both sides of the equator, result in stable confinement structures. Numerical modeling of charged particle orbits that pass through the regions of these local field minima has been carried out using different seasonal Earth tilt and different magnetospheric disturbance level. These orbit tracings show when and where these off-equatorial trapped radiation zones would be situated. The existence and extent of these confinement zones depend on the tilt angle. Indeed, the northern cusp confinement zone appears only at the northern summer solstice, while the southern cusp particle capture zone appears around winter solstice. The particle orbits that pass through opposite off-equatorial field minimum during solstices reveal a bound of the geomagnetic equatorial plane on the day sector. During equinox, the particle confinement zones exist in both cusps at times of disturbed magnetosphere conditions. The trapped particles drift within the trapping zones with periods of the several minutes, conserving the 1st and 2nd adiabatic invariants.


  • Antonova, A. E. and V. P. Shabansky, Structure of geomagnetic field at great distances from the Earth, Geomagn. Aeron., 8, 639, 1968.

    Google Scholar 

  • Antonova, A. E., Yu. I. Gubar, and A. P. Kropotkin, Energetic trapped particles in a Model Magnetic Field of the magnetospheric cusp, Geomagn. Aeron., 41, n1, 6–9, 2001.

    Google Scholar 

  • Antonova, A. E., Yu. I. Gubar, and A. P. Kropotkin, Effects in the radiation belts caused by the second adiabatic invariant violation in the presence of dayside off-equatorial magnetic field minima, Adv. Space Res., 31, n5, 1223–1228, 2003.

    Article  Google Scholar 

  • Chen, J., T. A. Fritz, R. B. Sheldon, et al., A new temporally confined population in the polar cap, Geophys. Res. Lett., 24, 1447, 1997.

    Article  Google Scholar 

  • Delcourt, D. C. and J.-A. Sauvaud, Recirculation of plasma sheet particles into high latitude boundary layer, J. Geophys. Res., 103(A11), 26521–26532, 1998.

    Article  Google Scholar 

  • Delcourt, D. C. and J.-A. Sauvaud, Populating of cusp and boundary layers by energetic (hundreds of keV) equatorial particles, J. Geophys. Res., 104(A10), 22635–22648, 1999.

    Article  Google Scholar 

  • Gusev, A. A. and G. I. Pugacheva, About output of quasi-trapped electrons from the atmosphere, Geomagn. Aeron., 22, 487–489, 1982.

    Google Scholar 

  • Karra, M. and T. Fritz, Energy dispersion features in the vicinity of the cusp, Geophys. Res. Lett., 26, 3553, 1999.

    Article  Google Scholar 

  • Kudela, K., V. N. Lutsenko, et al., High energy particle dispersion events observed by Interball-1,2, Adv. Space Res., 30, 2849, 2002.

    Article  Google Scholar 

  • Pissarenko, N. F., I. N. Kirpichov, V. N. Lutsenko, et al., Cusp energetic particles observed by Interball Tail Probe in 1996, Phys. Chem. Earth (C), 26, n1-3, 241–245, 2001.

    Google Scholar 

  • Roederer, J., Dynamics of Geomagnetically Trapped Radiation, SpringerVerlag, Heidelberg-New York, 1970.

    Book  Google Scholar 

  • Shabansky, V. P., Some processes in magnetosphere, Space Sci. Rev., 12(3), 299–418, 1972.

    Article  Google Scholar 

  • Sheldon, R. B., H. E. Spence, et al., The discovery of trapped energetic electrons in the outer cusp, Geophys. Res. Lett., 25, 1825, 1998.

    Article  Google Scholar 

  • Tsyganenko, N. A., Magnetospheric magnetic field with a warped tail current sheet, Space Sci. Rev., 37, 5, 1989.

    Article  Google Scholar 

  • Volland, H., A model of the magnetospheric electric convection field, J. Geophys. Res., 83, 2695, 1978.

    Article  Google Scholar 

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Correspondence to G. Pugacheva.

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Pugacheva, G., Gusev, A.A., Jayanthi, U.B. et al. Seasonal polar cap radiation zones in dayside magnetosphere. Earth Planet Sp 56, e17–e20 (2004).

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Key words

  • Magnetosphere
  • trapped particles
  • radiation belt
  • cusp