Main Results of Cosmic Ray Survey to Antarctica on the Ship Italica in 1996/97

Together with direct measurements of primary CR, either with space probes outside the geomagnetic field or with balloons in the upper atmospheric layers, the technique of continuous measurements of the secondary components by groundbased detectors is a unique source of information on the temporal variations of the CR distribution function external to the magnetosphere, as well as the cutoff rigidity planetary distribution. These variations contain important information on the dynamic processes in the Heliosphere and acceleration phenomena in the solar atmosphere; their study is an essential tool for determining the models appropriate to different modulation processes. A “great instrument” consisting of the geomagnetic field, the earth's atmosphere, and all the CR detectors located on the earth's surface provides a continuous monitoring of primary variations in a wide rigidity interval and for all directions of incoming particles out of the magnetosphere. The global-spectrographic method (Dorman, M1974; Belov et al., 1983) based on the knowledge of coupling functions (Dorman, M1957) furnishes an efficient mathematical tool for this purpose. The core of the “great instrument” is the worldwide network of CR neutron monitors, which are sensitive to temporal variations of primaries with rigidities up to ~40GV. The technique of latitude surveys of the CR nucleonic component is the most reliable method of calibrating the “CR geomagnetic spectrometer” and for determining the coupling functions needed for studying temporal variations of the primary CR spectrum using data from the neutron monitor station network (see the reviews in Dorman, M1974, M1975, M2004; also see Bachelet et al., 1965,1972, 1973; Dorman et al., 1966, 1967a, b, c; Lockwood and Webber, 1967; Kodama, 1968; Keith et al., 1968; Carmichael and Bercovitch, 1969; Allkofer et al., 1969; Alexanyan et al., 1979a, b, 1985; Potgieter et al., 1980a, b; Moraal et al., 1989; Nagashima et al., 1989; Stoker, 1993; Stoker and Moraal, 1995; Bieber et al., 1997; Villoresi et al., 1997, 1999). Moreover, with latitude surveys it is also possible to control the evaluation of geomagnetic cutoff rigidities and detect geomagnetic anomalies (see Stoker, 1995; Stoker et al., 1997; Clem et al., 1997). However, to obtain reliable latitudinal variations in the CR nucleonic component, it is necessary to apply refined analysis techniques to the raw data recorded along the survey. Papers by Villoresi et al. (1999, 2000), Iucci et al. (1999, 2000), and Dorman et al. (1999, 2000) describe the latitude survey experiment performed with neutron detectors on board the ship Italica during 1996/97, as part of the Italian Antarctic Research Program. An entire complex procedure was developed which we applied to produce valid reduced data and accurate determination of the coupling functions.