This hysteresis effect in Fig. 3.6.1 and 3.6.2 shows that the size of region of CR effective modulation for energy of few GeV is expected about 100 AU. On these great distances the energy density of IMF and moving solar wind became comparable with CR pressure, so the CR nonlinear effects are sufficient (see Sections 3.2 and 3.3)
3.6.2. Long - term CR spectrum modulation in the Heliosphere
The investigation of long-term CR modulation in the interplanetary space gives important information on dimensions of the Heliosphere (from hysteresis effect, see Section 3.6.1) as well as on the dependence of transport path A versus particle rigidity R (from long term CR rigidity spectrum of modulation). The time-dependence of the primary variations of CR with effective rigidities R = 2, 5, 10 and 25 GV was found by Belov, Dorman et al. (1988, 1990) on the basis of ground measurements (muon and neutron components) as well as measurements in stratosphere on balloons and in space on satellites and spacecrafts. Results are shown in Fig. 3.6.3.
Fig. 3.6.3. Time dependence of primary CR with effective rigidity R = 2, 5, 10 and 25 GV (on the basis of ground level registration of muon and neutron components and measurements on balloons and satellites).
The smaller modulation in the 1965-1975 solar activity cycle reflects the influence of the reversal o the general magnetic field of the Sun (drift effects). Fig. 3.6.4 shows the observed rigidity spectrum of long-term modulation relative to the minimum of solar activity in 1965 as well as the residual modulation spectrum in
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