Abstract
An analysis is made of the long-period geomagnetic pulsations as recorded at seven Norilsk meridian stations (λ=162°, latitudinal range: 61°â71°N) following abrupt magnetospheric expansion during the storm of 22 March 1979 caused by a rapid decrease in solar wind density. As with the time interval following an abrupt contraction at the time of sudden storm commencement, there exist two types of pulsations in the pulsation spectra: latitude-independent (T>400 s) and latitude-dependent (T<200 s) pulsations. The first pulsation type is interpreted in terms of forced pulsations associated with magnetopause oscillations. The oscillation period is determined by plasma density in the boundary layer and by the radius of the magnetosphere (T ~ ρ1/2R4). The latitudinal dependence of the period, amplitude and polarization of the second-type pulsations is in agreement with the resonance mechanism of their origin.Keywords. Geomagnetic pulsations · Solar wind · Magnetopause oscillations
Highlights
Abrupt changes in solar wind dynamic pressure during sudden storm commencements (SSC) and sudden impulses (Si) lead to the excitation of a broad spectrum of decaying geomagnetic pulsations (Psc) (Saito and Matsushita, 1967)
Our study considers the regime of generation of Psc5 by a negative pressure impulse of 22.03.1979, as well as discussing the excitation mechanism for global oscillations of the magnetosphere
At 1009:30 UT there was an abrupt decrease in solar wind density and pressure, which led to a displacement of the magnetopause from the Earth from
Summary
Abrupt changes in solar wind dynamic pressure during sudden storm commencements (SSC) and sudden impulses (Si) lead to the excitation of a broad spectrum of decaying geomagnetic pulsations (Psc) (Saito and Matsushita, 1967). A number of regularities have been established and explained; the question of identifying the global magnetosonic mode still is a widely debated topic This mode, corresponding to the Pc5 range, must be excited on the external L-shell of the magnetosphere with equal probability by both positive and negative pressure impulses of the solar wind (Southwood and Kivelson, 1990). Parkhomov et al.: Long-period geomagnetic pulsations caused by the solar wind negative pressure impulse
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