Abstract—
This paper analyzes the effect of azimuthal proton drift from the nighttime sector of the Earth’s magnetosphere on the characteristics of the pitch-angle anisotropy of proton fluxes in the daytime sector. The drift in the magnetic field caused by curvature of the field lines and the magnetic field gradient, in the absence of external forces, has been considered. The external geomagnetic field has been described with Tsyganenko’s T96 model. The proton drift has been calculated in the approximation of the guiding center motion in the equatorial magnetosphere plane, i.e., after averaging over the bounce oscillations of particles between the mirror points. The influence of two effects on the anisotropy value has been studied. The first effect is related to changes in the proton pitch angle in the course of azimuthal drift. This effect can significantly (up to approximately six times, depending on the T96 model input parameters) increase the transverse anisotropy of protons when they drift from the nighttime to the daytime side. The second effect is caused by drift-shell splitting, as a result of which protons from the nighttime sector from different radial distances come to the same field line on the daytime side: the lower the pitch angle of the particle is, the larger is the distance it starts to drift from. As a result, the radial proton flux gradient on the magnetosphere nighttime side can lead to a pitch-angle anisotropy of fluxes in the daytime sector that is sufficient to generate electromagnetic ion cyclotron (EMIC) waves, even if the fluxes in the nighttime sector were isotropic in the pitch angles. The dependence of this anisotropy on the radial proton flux gradient on the nighttime side has been studied. The maximum anisotropy in the daytime sector due to the longitudinal drift in the geomagnetic field can be achieved at a distance of 5.3–10 RE depending on the Т96 model input parameters.
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REFERENCES
Allen, R.C., Zhang, J.-C., Kistler, L.M., Spence, H.E., Lin, R.-L., Klecker, B., Dunlop, M.W., André, M., and Jordanova, V.K., A statistical study of EMIC waves observed by Cluster: 1. Wave properties, J. Geophys. Res.: Space Phys., 2015, vol. 120, pp. 5574–5592. https://doi.org/10.1002/2015JA021333
Anderson, B.J., Erlandson, R.E., and Zanetti, L.J., A statistical study of Pc1–2 magnetic pulsations in the equatorial magnetosphere: 1. Equatorial occurrence distributions, J. Geophys. Res., 1992, vol. 97, no. A3, pp. 3075–3088. https://doi.org/10.1029/91JA02706
Ganushkina, N.Yu., Liemohn, M.W., and Pulkkinen, T.I., Storm-time ring current: Model-dependent results, Ann. Geophys., 2012, vol. 30, pp. 177–202. https://doi.org/10.5194/angeo-30-177-2012
Hamlin, D.A., Karplus, R., Vik, R.C., and Watson, K.M., Mirror and azimuthal drift frequencies for geomagnetically trapped particles, J. Geophys. Res., 1961, vol. 66, pp. 1–5. https://doi.org/10.1029/JZ066i001p00001
Kennel, C.F. and Petschek, H.E., Limit of stably trapped particle fluxes, J. Geophys. Res., 1966, vol. 71, no. 1, pp. 1–28. https://doi.org/10.1029/JZ071i001p00001
Lubchich, A.A. and Semenova, N.V., Modeling of the electromagnetic ion cyclotron wave generation in the H+–He+ plasma of the inner magnetosphere, J. Atmos. Sol-Terr. Phys., 2015, vol. 125–126, pp. 21–37. https://doi.org/10.1016/j.jastp.2015.02.004
Lubchich, A.A., Yahnin, A.G., Titova, E.E., Demekhov, A.G., Trakhtengerts, V.Yu., Manninen, J., and Turunen, T., Longitudinal drift of substorm electrons as the reason of impulsive precipitation events and VLF emissions, Ann. Geophys., 2006, vol. 24, no. 10, pp. 2667–2684. https://doi.org/10.5194/angeo-24-2667-2006
Lyubchich, A.A., Demekhov, A.G., Titova, E.E., and Yahnin, A.G., Amplitude–frequency characteristics of ion–cyclotron and whistler-mode waves from Van Allen Probes data, Geomagn. Aeron. (Engl. Transl.), 2017, vol. 57, no. 1, pp. 40–50. https://doi.org/10.7868/S0016794017010084
McCollough, J.P., Elkington, S.R., and Baker, D.N., The role of Shabansky orbits in compression-related electromagnetic ion cyclotron wave growth, J. Geophys. Res., 2012, vol. 117, A01208. https://doi.org/10.1029/2011JA016948
Meredith, N.P., Horne, R.B., Kersten, T., Fraser, B.J., and Grew, R.S., Global morphology and spectral properties of EMIC waves derived from CRRES observations, J. Geophys. Res.: Space Phys., 2014, vol. 119, pp. 5328–5342. https://doi.org/10.1002/2014JA020064
Min, K., Lee, J., Keika, K., and Li, W., Global distribution of EMIC waves derived from THEMIS observations, J. Geophys. Res., 2012, vol. 117, A05219. https://doi.org/10.1029/2012JA017515
Noh, S.-J., Lee, D.-Y., Choi, C.-R., Kim, H., and Skoug, R., Test of ion cyclotron resonance instability using proton distributions obtained from Van Allen Probe-A observations, J. Geophys. Res.: Space Phys., 2018, vol. 123, pp. 6591–6610. https://doi.org/10.1029/2018JA025385
Reeves, G.D., Belian, R.D., and Fritz, T.A., Numerical tracing of energetic particle drifts in a model magnetosphere, J. Geophys. Res., 1991, vol. 96, no. A8, pp. 13997–14008. https://doi.org/10.1029/91JA01161
Roederer, J.G., Dynamics of Geomagnetically Trapped Radiation, New York: Springer, 1970. https://doi.org/10.1007/978-3-642-49300-3.
Sagdeev, R.Z. and Shafranov, V.D., On the instability of a plasma with an anisotropic distribution of velocities in a magnetic field, Sov. Phys. JETP, 1961, vol. 12, no. 1, pp. 130–132.
Saikin, A.A., Zhang, J.-C., Allen, R.C., Smith, C.W., Kistler, L.M., Spence, H.E., Torbert, R.B., Kletzing, C.A., and Jordanova, V.K., The occurrence and wave properties of H+-, He+-, and O+-band EMIC waves observed by the Van Allen Probes, J. Geophys. Res.: Space Phys., 2015, vol. 120, pp. 7477–7492. https://doi.org/10.1002/2015JA021358
Semenova, N.V., Yahnina, T.A., Yahnin, A.G., and Demekhov, A.G., Global distribution of energetic proton precipitations equatorward of the boundary of isotropic fluxes, Geomagn. Aeron. (Engl. Transl.), 2017, vol. 57, no. 4, pp. 398–405. https://doi.org/10.7868/S0016794017040174
Semenova, N.V., Yahnin, A.G., Yahnina, T.A., and Demekhov, A.G., Properties of localized precipitation of energetic protons equatorward of the isotropic boundary, Geophys. Res. Lett., 2019, vol. 46, no. 20, pp. 10932–10940. https://doi.org/10.1029/2019GL085373
Shabansky, V.P., Some processes in magnetosphere, Space Sci. Rev., 1971, vol. 12, no. 3, pp. 299–418. https://doi.org/10.1007/BF00165511
Shabansky, V.P., Yavleniya v okolozemnom prostranstve (Near-Earth Space Phenomena), Moscow: Nauka, 1972.
Shukhtina, M.A. and Sergeev, V.A., Modeling the drift of energetic particles in the real magnetosphere near a geosynchronous orbit, Geomagn. Aeron., 1991, vol. 31, no. 5, pp. 775–780.
Shukhtina, M.A., On the calculation of the magnetic drift velocity of particles with arbitrary pitch angles, Planet. Space Sci., 1993, vol. 41, no. 4, pp. 327–331. https://doi.org/10.1016/0032-0633(93)90028-Z
Takahashi, K., Anderson, B.J., Ohtani, S., Reeves, G.D., Takahashi, S., Sarris, T.E., and Mursula, K., Drift-shell splitting of energetic ions injected at pseudo-substorm onsets, J. Geophys. Res., 1997, vol. 102, pp. 22117–22130. https://doi.org/10.1029/97JA01870
Tsyganenko, N.A., A magnetospheric magnetic field model with a warped tail current sheet, Planet. Space Sci., 1989, vol. 37, no. 1, pp. 5–20. https://doi.org/10.1016/0032-0633(89)90066-4
Tsyganenko, N.A., Modeling the Earth’s magnetospheric magnetic field confined within a realistic magnetopause, J. Geophys. Res., 1995, vol. 100, no. A4, pp. 5599–5612. https://doi.org/10.1029/94JA03193
Tsyganenko, N.A., Effects of the solar wind conditions in the global magnetospheric configurations as deduced from data-based field models, in Proceedings of the 3rd International Conference on Substorms (ICS-3), Versailles, France, 12–17 May 1996 (ESA SP-389), Rolfe, E.J. and Kaldeich, B., Eds., Paris: European Space Agency, 1996, pp. 181‒185.
Tsyganenko, N.A. and Usmanov, A.V., Determination of the magnetospheric current system parameters and development of experimental geomagnetic field models based on data from IMP and HEOS satellites, Planet. Space Sci., 1982, vol. 30, pp. 985–998. https://doi.org/10.1016/0032-0633(82)90148-9
Wang, C.-P., Zaharia, S.G., Lyons, L.R., and Angelopoulos, V., Spatial distributions of ion pitch angle anisotropy in the near-Earth magnetosphere and tail plasma sheet, J. Geophys. Res.: Space Phys., 2013, vol. 118, pp. 244–255. https://doi.org/10.1029/2012JA018275.
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The work was supported by the Russian Science Foundation, project no. 15-12-20005.
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Translated by E. Maslennikova
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Lyubchich, A.A., Demekhov, A.G. & Yahnin, A.G. Characteristics of the Pitch-Angle Anisotropy of Energetic Protons in the Daytime Magnetosphere due to Particle Drift in the Nondipole Magnetic Field. Geomagn. Aeron. 60, 461–471 (2020). https://doi.org/10.1134/S001679322004009X
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DOI: https://doi.org/10.1134/S001679322004009X