Plasmasphere structure obtained from geomagnetic pulsation data☆

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 Earth's 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.