On the origin of the cusp field-aligned currents
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Vols. 1-18 (1924-1944), ISSN 0044-2801
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Abstract
A complicated system of field-aligned currents is known to exist in the high-latitude region near noon, associated with the cusp. We suggest that the equatorward part of this system, referred to as the Region 1 field-aligned currents, is caused by the leakage of the field-aligned currents associated with the rotational discontinuities at the dayside magnetopause. The poleward part, referred to as the cusp field-aligned currents, is associated with the tail magnetopause. In this situation, it can be shown that the direction of the field-aligned currents at the magnteopause is controlled by the y-component of the interplanetary magnetic field (By). The poleward (equatorward) part of this field-aligned current system is found to flow out of (into) the northern polar ionosphere when By > 0 and into (out of) the northern ionsophere when By < 0. This current pattern reverses systematically in the southern polar ionosphere. Therefore, the suggested mechanism can explain qualitatively the observed changes of the cusp current systems. Further, the latitudinal width of the cusp field-aligned current system at the ionospheric altitude is estimated to be 100-400 km, consistent with observations.
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References
Akasofu, S.-I., Roederer, M. (1984) Dependence of the polar cap geometry on the IMF. Planet. Space Sci. 32:111-115
Banks, P.M., Araki, T., Clauer C.R., St. Maurice, J.P., Foster, J.C. (1984) The interplanetary electric field, cleft currents and plasma convection in the polar caps. Planet. Space Sci. 32:1551-1557
Berchem, J., Russell, C.T. (1982) Magnetic field rotation through the magnetopause: ISEE 1 and 2 observations. J. Geophys. Res. 87:8139-8148
Bythrow, P.F., Potemra, T.A., Hoffman R.A. (1982) Observations of field-aligned currents lparticles, and plasma drift in the polar cusps near solstice. J. Geophys. Res. 87:5131-5139
Cowley, S.W.H. (1981) Magnetospheric asymmetries associated with the y-component of the IMF. Planet. Space Sci. 29:79-96
D'Angelo, N. (1980) Field-aligned currents and large scale magnetospheric electric field.s Ann. Geophys. 36:31-39
Doyle M.A., Rich, F.J. Burke, W.J., Smiddy, M. (1981) Field-aligned currents and electric fields observed in the region of the dayside cusp. J. Geophys. Res. 86:5656-5664
Friis-Christensen, E., Kamide, Y., Richmond, A.D., Matsushita, S. (1985) IMF control of high latitude electric fields, ionospheric and Birkeland currents determined from Greenland magnetometer data. J. Geophys. Res. 90:1325-1338
Heikkila, W.J. (1984) Magnetospheric topology of fields and currents. In: Potemra, T.A. (Ed.) Magnetospheric currents, p 208-222. Washington, D.C.: American Geophys. Union
Iijima, T., Fujii, R., Potemra, T.A., Saflekos, N.A. (1978) Field-aligned currents in the south polar cusp and their relationship to the interplanetary magnetic field. J. Geophys. Res. 83:5595-5603
Iijima, T., Potemra, T.A. (1976) Field-aligned currents in the dayside cusp observed by Triad. J. Geophys. Res. 81:5971-5979
Kaufman, R.L., Cahill, L.J., Jr. (1977) The magnetopause at 5.2 RE on August 4, 1972: Magnetopause shape and structure. J. Geophys. Res. 82:1573-1584
Lee, L.C., Kan, J.R. (1979) A unified kinetic model of the tangential magnetopause structure. J. Geophys. Res. 84:6417-6426
Lee, L.C., Kan, J.R. (1982) Structure of the magnetopause rotational discontinuity. J. Geophys. Res. 87:139-143
McDiamid, I.B., Burrows, J.R., Wilson, M.D. (1978) Magnetic field perturbations in the dayside cleft and their relationship to the IMF. J. Geophys. Res. 83:5753-5756
McDiamid, I.B., Burrows, J.R., Wilson, M.D. (1979) Large-sclae magnetic field perturbations and particle measurements at 1400 km on the dayside. J. Geophys. Res. 84:1431-1441
Primdahl, F., Spangslev, F. (1981) Cusp region and auroral zone fieldaligned currents. Ann. Geophys. 37:529-538
Reiff P.H., Burch, J.L., Heelis, R.A. (1978) Dayside auroral arcs and convection. Geophys. Res. Lett. 5:391-394
Rosenbauer, H., Grunwaldt, H., Montgomery, M.D., Paschmann, G., Sckopke, N. (1975) HEOS 2 plasma observations in the distant polar magnetosphere: The plasma mantle. J. Geophys. Res. 80:2723-2737
Rostoker, G. (1980) Magnetospheric and ionospheric currents in the polar cusp and their dependence on the BY component of the interplanetary magnetic fields. J Geophys. Res. 85:4167-4176
Russell, C.T., Elphic, R.C. (1978) Initial ISEE magnetometer results: magnetopause observations. Space Sci. Rev. 22:681-715
Sonnerup, B.U.O., Paschmann, G., Papamastorakis, I., Sckopke, N., Haerendel, G., Bame, S.J., Asbridge, J.R., Gosling, J.T., Russell, C.T. (1981) Evidence for magnetic field reconnection at the Earth's magnetopause. J. Geophys. Res 86:10049-10067
Swift, D.W., Lee, L.C. (1983) Rotation discontinuities and the structure of the magnetopause. J. Geophys. Res. 88:111-124
Wang, D.J., Sonnerup, B.U.O. (1984) Electrostatic structure of the rotational discontinuity II: Shock pair solutions 27:2828-2834
Wilhjelm, J., Friis-Christensen, E., Potemra T.A. (1978) The relationship between ionospheric and field-aligned currents in the dayside cusp. J. Geophys. Res. 83:5586-5594