Latitude, altitude and primary modulation effects on the multiplicity distribution in the NM-64 neutron monitors

Multiplicity data obtained from the NM-64 neutron monitors of Rome and Leeds during the years 1967/68/69 are analyzed together with those from the European survey done in Summer 1969 with a standard 3NM-64. The attenuation coefficients for different multiplicities have been estimated; the variations of these coefficients with multiplicity, latitude and altitude are found to be generally in agreement with other experimental and theoretical results. The latitude curves of the multiplicity intensities obtained from 0.8 to 6.3 GV are compared with those reported by Kodama and Inoue (1970). The primary modulations effect on the multiplicity distribution is studied in the case of sixteen Forbush decreases; an exponent k=0.7 is obtained on the hypothesis of a power law for the modulation function.