N. Iucci et al., Short and long-term variations in the cosmic ray intensity and their connection with the 5303 Å coronal line intensity in solar cycle No. 20, Laboratorio di Ricerca e Tecnologia per lo Studio del Plasma nello Spazio , LPS-73(8), 1973, pp. 1-33
The cosmic ray modulation in the period 1965.70 is investigated by the comparison of the intensity data of groundbased stations with different response to primaries. The socalled step-like modulation, already observed by other authors, is found to be produced by the overlapping between the quasi-stationary solar cycle modulation and the Forbush decrease events. Moreover a good correlation between the cosmic-ray variance (Forbush decrease index) and the 5303 coronaI intensity at middle heliolatitudes (17.5°+42.5°) is found, while the quasi-stationary solar cycle modulation is well correlated with the 5303 intensity near the solar equator (0°+17.5°). The different time behaviour of the solar activity at different heliolatitudes causes the step-like modulation.