The Empirical Implication of Conducting a Chree Analysis Using Data from Isolated Neutron Monitors

Investigation of Forbush Decreases and Other Solar/Geophysical Agents Associated With Lightning Over the U.S. Latitude Band and the Continental Africa

“…The FD detection program developed by Okike and Umahi (; Paper 2 hereafter) is adapted and employed for event selection in the present work. While the algorithm was tested using CR data for 1 year (year 2005) in Paper 2, two solar cycles (22 (1986–1996) and 23 (1996–2008)) are used here to further validate the algorithm.…”

“…Following the indications of Chronis () and Scott et al () on the possible influence of other planetary variables on lightning and meteorological data, we examined the relations between the FDs and lightning and other solar and meteorological data presented in Tables and . The FD key dates and magnitudes in Tables and could provoke a lot of discussions with regard to the use of data from isolated neutron monitor (Okike & Umahi, ) as well as the nature of the FDs. Although we do not intend to conduct individual examination of the FDs, a close inspection of the two tables shows that 14 out of the 30 (i.e., 47%) FDs in Table defined a different date from those of Table .…”

“…This fairly involved analysis procedure is used not only to remove the diurnal variation and anisotropy but also to account for the linear trends in the cosmic ray intensity arising from long‐term secular and periodic modulations, such as the solar modulation cycle (Bieber & Chen, ). We use Fourier transform technique and an R program in our attempt to calculate the FD amplitude and time of minimum depression in the GCR intensity (see; Okike & Umahi, , for methodological details).…”

“…For African continent, FDs are selected from Harmanus observatory, while Climax data are used for both North American continent and the U.S. latitude band. This is because GCRs are not uniformly distributed over the Earth, giving rise to simultaneous and nonsimultaneous FDs (Oh et al, ; Okike & Collier, ; Okike & Umahi, ).…”

“…CR detectors vary greatly in their characteristics. Okike and Umahi () indicated that these differences should be taken into account in the Chree method of analysis, where Forbush events are commonly used as the key parameters. A review of the existing publications shows that some researchers do not account for these dissimilarities.…”