INTERMITTENCY IN THE MIDLATITUDE Pi2 PULSATIONS OBSERVED DURING THE MAGNETOSPHERIC SUBSTORMS AND IN THEIR ABSENSE
The results of investigation of distributions of amplitudes and durations of time intervals between wave packets of Pi2-type geomagnetic pulsations observed at nighttime during the development and the absence of magnetospheric substorms are presented. The analog recordings of the mid-latitudinal Borok observatory (geographical coordinates φ= 58.03°; <i>X= </i>38.97°) for 1995, 1997 were used in the investigation. Three groups of pulsations are explored: 1) Pi2 observed during substorms connected with an external action on the magnetosphere, 2) Pi2 observed during substorms which occurred spontaneously and 3) Pi2 observed during the absence of substorms on the night side of the magnetosphere. As possible triggers of the magnetospheric substorms the IMF <i>B</i>y and <i>Bz </i>components and the solar wind dynamic pressure <i>pV</i><sup><i>2</i></sup><i> </i>were considered. It was shown that distributions of pulsation amplitudes and durations of intervals between Pi2 bursts are approximated by power and exponential functions, respectively, which is typical for intermittent processes. The hypothesis that processes of the magnetospheric plasma turbulization can be one of the sources of Pi2 pulsation bursts is advanced. It is supposed that on the basis of the obtained indices it is possible to qualitatively estimate a degree of plasma turbulence on the night side of the magnetosphere during excitation of a sequence of Pi2 wave packets.