Investigation of heliosphere, i.e., the sphere of manifestation of solar activity, is one of the most important areas of research in modern space physics. A remarkable feature of the solar activity is its cyclicity, i.e., the quasi-periodic appearance and development of active regions. The most obvious example of manifestation of the solar cycle is a variation in the number, of sun-spots with the average period of 11 years (Fig. I). A striking example of the effect of the solar activity on processes occurring in the heliosphere is the modulation of galactic cosmic rays (GCRs) by the solar wind in the vicinity of the Earth: the intensity of GCRs can decrease by an order of magnitude, remaining in anti-correlation with the solar activity (see the results of long-term probing of the stratosphere [1] presented in Fig. 1). In standard models describing the modulation of GCRs crossing the solar wind, their flux is affected by the action of various processes. These are transport processes of diffusion through turbulent magnetic fields, convective processes associated with magnetic fields frozen into the solar wind, and the cooling caused by the expansion of the solar wind volume with distance from the Sun [2, 3J. It is natural to expect that the boundary of the GCR modulation region corresponds to the dynamic boundary between the solar wind and the interstellar gas. The position of this boundary can be estimated provided that the GCR intensity gradients in the heliosphere are known. In order to separate, wherever possible, the galactic component of cosmic rays from the solar component, spacecraft, in most cases, were launched in years of minimal solar activity, when the intensity level of GCRs in the heliosphere was the highest. The results obtained invariably led to small [on the order of -2-4% per astronomical unit (AU)] gradients of GCRs with an energy of E > 100 MeV.
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