Variation of the Forbush-decrease rigidity spectrum with the cycles of solar activity

The data of the worldwide neutron monitor station network for 1965-1994 are used to study the variation of the rigidity spectrum of Forbush decreases in the cosmic-ray intensity with the cycles of solar activity. The results obtained reveal the dependence of the rigidity spectrum on the phase of sol ar cycle. The established connection of the spectrum index value with the r elative energy of the large-scale turbulence of the magnetic field that dep ends on the solar activity level shows that the formation of the rigidity s pectrum of cosmic-ray decreases may be due to the state of the interplaneta ry magnetic field. The authors revealed no explicit dependence of the spect rum of Forbush decreases on the shock velocity and heliocoordinates of sola r flares.