O.M. Raspopov

The possible way of determining the plasmasphere parameters by the geomagnetic pulsations amplitude

Abstract A statistical analysis of geomagnetic pulsations within the periods of T = 10 to 200 sec at the meridional network of stations in conditions of moderate geomagnetic activity has been carried out which shows that the middle latitude maximum, the subauroral minimum and the high latitude maximum are the inherent property of the geomagnetic pulsation amplitude distribution along the meridional profile. Within the framework of the simplest model problem of magnetosonic disturbance propagation in the geomagnetic equatorial plane it is shown that magnetic disturbance amplitude is inversely proportional to the local value of the Alfven velocity, and the middle latitude amplitude maximum coincides with the Alfven velocity minimum, whereas the amplitude minimum is located on the Southern boundary of the regions of the maximum gradient of the cold plasma density (plasmapause). From such a point of view it is possible to obtain data on the cold plasma distribution in the plasmasphere from those on the geomagnetic pulsation amplitude distribution along the meridional profile.

Plasmasphere structure obtained from geomagnetic pulsation data

Abstract A distribution of geomagnetic pulsation amplitudes (T ⩾ 30 sec) has been analyzed during substorm development on the basis of data from a meridional network of stations spaced approximately at ΔΦm = 1° within the range of geomagnetic latitudes from 53° to 65°. Besides the previously known peculiarities of the meridional distribution of pulsation amplitudes, i.e. the existence of high-latitude (Φm ≈ 62–67°) maxima, as well as the subauroral minimum (Φm ≈ 58–59°) in amplitude, the formation and the development of an intermediate amplitude maximum adjacent to the high-latitude maximum and located between it and the subauroral minimum, at Φm~ 60–61° have been discovered. The location of the intermediate maximum is coincident with the centre of the trough in the concentration of particles in the ionospheric F2-layer and with the statistical position of the plasmapause projection to the Earths surface. The transference of the position of the intermediate maximum to lower latitudes during substorms has been discovered. On the supposition that these transferences are the result of the cold plasma convection it was possible to evaluate the large-scale electric field in the magnetosphere during a substorm: E ~ 1.10−5V/cm.