In this report, the calculation of riometer absorption during several PCA events of particular interest is presented. These calculations are based on earlier work in which an improved effective recombination coefficient was derived and an atmospheric model for (1) each month of the year, (2) day and night, and (3) 60 deg N and 90 deg N latitude was presented. In this report, the calculated values of riometer absorption are presented for 5 PCA events: 2 Nov. 69, 7 Mar. 70, 25 Jan. 71, 2 Sep. 71, and 3 Aug. 72. The calculated values of riometer absorption are compared with experimental values measured for both day and night conditions at Thule, Greenland. An approximate connection between riometer absorption and the square-root of the proton flux for nighttime conditions is presented. This relationship, which has previously been applied only for daytime conditions, is discussed both on a fundamental level and on the level of verification by comparison with experiment. In addition, the basic equation widely used to calculate riometer absorption is compared with the original Sen-Wyller result.