Differential response and specific yield functions of cosmic-ray neutron monitors

Abstract

From the recent neutron monitor latitude survey by H. Carmichael and from the primary spectrum measurements by W. Webber both at solar minimum, we have deduced new differential response and specific yield functions of cosmic‐ray neutron monitors located at sea level and mountain elevations with vertical cutoff rigidities in the interval 0.7 < Pc < 10 Gv. The differential response functions at sea level are larger than the previously calculated values at rigidities P < 3 Gv. The proton specific yield function at sea level is obtained and can be represented by KP+2.6 for 2.5 < P < 6 Gv. The relative contributions of primary nuclei with Z ≥ 2 to the counting rate of a sea‐level neutron monitor as a function of Pc are evaluated. The change in the differential response functions between 1963 and 1965 has been used to determine the change in the primary differential cosmic‐ray spectrum. The decrease in the observed differential primary spectrum agrees well with the decrease in the neutron differential response function in the rigidity range where they can be compared.

Cosmic ray detector response to transient solar modulation: Forbush decreases

“…[10] R m values computed by us for NM sites at different atmospheric depths (using Lockwood and Webber [1967]) and others are listed in Table 2; we include R m = 67 GV for ionization chamber (IC) at Yakutsk computed by Fujimoto et al [1984]. One notes that there is no correlation between R m and R o values for GCR rigidities 1.1 GV.…”

“…At higher rigidities, it is usual to assume that the slope of W is continuous and NM differential response curves are extended using a power law with a negative exponent (Àg). The reader may refer to the paper of Lockwood and Webber [1967] for curve-extending details. For a sea-level NM (1030 g/cm 2 ), they give g = 1.57; for a mountain site (680 g/cm 2 ), g = 1.75, etc.…”

“…[7] Earlier, we used the differential response curves of Lockwood and Webber [1967] and Bachelet et al [1973] to compute R m values for several NM sites Sabbah, 1993a,1993b;Ahluwalia and Fikani, 1996]. Additional R m values for global sites are added to the list in this paper.…”

“…For sea level, Lockwood and Webber derive response from the latitude survey conducted in Canada, USA, and Mexico in the summer of 1965 by Carmichael et al [1965] using NM-64, along with additional data obtained in Canada in December 1965 (see the paper of Lockwood and Webber [1967] for details).…”

“…[9] In prior work, we computed R m values from the differential response curves given by Lockwood and Webber [1967] at different elevations as a function of R o (see Figure 6 of their paper). For sea level, Lockwood and Webber derive response from the latitude survey conducted in Canada, USA, and Mexico in the summer of 1965 by Carmichael et al [1965] using NM-64, along with additional data obtained in Canada in December 1965 (see the paper of Lockwood and Webber [1967] for details).…”