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Time variation analysis of the daily Forbush decrease indices
Authors:Sankar Narayan Patra  Koushik Ghosh  Subhash Chandra Panja
Institution:(1) Institute of Experimental Physics, SAS, W, atson Str. 47, 04353 Koscaronice, Slovakia;(2) IFSI/CNR, Via del Fosso del Cavaliere 100, 00133 Rome, Italy;(3) Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland;(4) IZMIRAN, 142 092 Troitsk (Moscow), Russia
Abstract:In the present paper we have analyzed the daily Forbush decrease indices from January 1, 1967 to December 31, 2003. First filtering the time series by Simple Exponential Smoothing, we have applied Scargle Method of Periodogram on the processed time series in order to search for its time variation. Study exhibits periodicities around 174, 245, 261, 321, 452, 510, 571, 584, 662, 703, 735, 741, 767, 774, 820, 970, 1062, 1082, 1489, 1715, 2317, 2577, 2768, 3241 and 10630 days with confidence levels higher than 90%. Some of these periods are significantly similar to the observed periodicities of other solar activities, like solar filament activity, solar electron flare occurrence, solar-flare rate, solar proton events, solar neutrino flux, solar irradiance, cosmic ray intensity and flare, spectrum of the sunspot, solar wind, southern coronal hole area and solar cycle, which may suggest that the Forbush decrease behaves similarly to these solar activities and these activities may have a common origin.
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