2. Initial Data

[7]  To study giant pulsations, multiyear continuous analog recordings of the magnetic field (the code and corrected geomagnetic coordinates are shown in the parentheses) at the auroral observatory Molodezhnaya (MOL, F'=-66.7^o, l'=76.0^o ) for 1981-1992 with the recording rate of 90 mm h ^-1 (the data are archived at the Geophysical Observatory Borok) were used. For the analyzed period (11 years) we found 30 events of observations of the Pg pulsations observed as one wave packet. The initial magnetograms were scanned and presented in a digital form with the discreteness step of 5 s. The creation of the wave packets envelopes amplitude of the Pg pulsations was based on application of the Gilbert transformation [Vainshtein and Vakman, 1983]. To do this, we transformed the initial signal into analytical signal:

where X(t) is the initial signal, Y(t) is the Gilbert transformation of the initial signal, and t is time. The amplitude envelope ( h(t) ) of Pg pulsations was found from

To analyze the interplanetary conditions in which the Pg pulsations were observed in MOL, we attracted the hourly data on the parameters of the solar wind and IMF from the digital King catalog (the WDCB 2, Moscow).