Barometric Coefficient Calculation
The method of defining the barometric
coefficient of the different components of secondary cosmic rays has been
studied by many authors in the past (
(1),
where dN is
the change of detector counting rate (due to pressure change), dP is the change of pressure and β is the barometric
coefficient. By integrating this expression and supposing that for pressure
=>
(2),
where P is the current atmospheric pressure.
The equation (2) is valid when the incoming cosmic ray flux is stable, so any variation of the detector counting rate is only due to the change of barometric pressure. In the case that there are variations in the cosmic ray flux, the equation (2) has the form:
=>
(3),
where ν is the variation of the cosmic ray flux. In order to calculate the variation ν, the corrected for pressure data of a reference station (S) are used (Chiba, 1976). The station (S) should have similar cut-off thresholds to the main station in order to assume that they both have similar cosmic ray spectra. The primary variation of cosmic rays for the reference station is:
(4)
Since equation (4) includes the corrected for pressure data of the reference station, the change to ν is only related to the change of cosmic ray flux. In order to transform the primary variation of the reference station to the variation of the main station, coupling coefficients are used (Belov et al., 1993). If the coupling coefficients of the zero harmonic are C0 and C0S for the main and reference station respectively, equation (3) becomes:
(5)
Equations (2)
and (5) can be used to experimentally calculate the barometric coefficient β by
applying a linear regression on the measured values of N and P for a specific
time period. The parameters No and
