1. Introduction

[2]  The giant pulsations (Pg) are known since the beginning of the last century [Birkeland, 1901; Rolf, 1931] and have been studied in a huge number of publications. During the recent 25 years the Pg pulsations were actively studied using the data of magnetometer chains [Chisham and Orr, 1991; Chisham et al., 1990, 1997; Green, 1979, 1985; Rostoker et al., 1979], auroral radars [Poulter et al., 1983], and spacecraft [Engebretson et al., 1988; Takahashi et al., 1992]. The relation of Pg to other phenomena has been also studied [Chisham et al., 1990; Taylor et al., 1989].

[3]  The Pg pulsations belong to rarely encountered phenomena localized by latitude and longitude of observations, and they differ from other types of geomagnetic pulsations by the regularity of their periods and by drop-like shape. The highest frequency of Pg occurrence corresponds to the dawn sector of the auroral oval [Rostoker et al., 1979]. The Pg are mainly registered in the conditions of a quiet magnetosphere ( Kp 0-2 ), in the equinox seasons in the years of solar activity minimum [Brekke et al., 1987]. As a rule, the mean duration of a Pg regime is 30-150 min, their typical periods belong to the Pc4 range, and the amplitude is of the order of 10-30 nT. The most typical feature of the Pg is their dominant polarization at the D component [Chisham et al., 1997; Green, 1979].

[4]  In spite of the fact that spatial, time, spectral, and polarization characteristics of the Pg pulsations are studied in detail, till now there is no commonly accepted point of view on their origin. The Alfvén waves generated as a result of a drift instability at the outer boundary of the ring current are considered as one of Pg excitation mechanisms [Green, 1979]. The other mechanism of Pg generation they often relate to bounce resonance of the protons of the ring current [Chisham, 1996; Chisham and Orr, 1991; Poulter et al., 1983; Takahashi et al., 1992]. Since the Pg frequency coincides with the bounce oscillations of protons [Chisham, 1996], some authors suggested that some role in the Pg pulsation generation may be played by protons and presented theoretical estimates of the proton energy. For example, Poulter et al. [1983] suggested that Pg may be a result of the bounce resonance instability of the protons with energies of ~10 keV. Chisham [1996] showed an existence of possible relation between the Pg pulsations and protons with energies of about 5-30 keV. However, as far as we know, no measurements of the energy of the precipitating protons during observations of giant pulsations have been conducted. Therefore there is no experimental confirmation of correlation of the probability of the Pg pulsation observations to fluxes of energetic protons. At the same time it is grounded theoretically and proved experimentally that high-energy protons participate in excitation of some types of more high-frequency pulsations (for example, of the Pc1 and Pc1,2) [Guglielmi, 1979; Matveeva et al., 1972; Yahnina et al., 2002]. From our point of view the detection of the relation of Pg to other types of geomagnetic pulsations would have been very useful for understanding of the mechanisms of the Pg pulsation generation. However, no studies of the correlation of Pg with geomagnetic pulsations of other frequency ranges have been performed. In this paper an attempt to study possible relation between the giant pulsations and high-frequency pulsations in the range (0.5-2.0) Hz is undertaken.