Short-term periodicities in interplanetary, geomagnetic and solar phenomena during solar cycle 24
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In this paper we study the quasi-periodic variations of sunspot area/number, 10.7 cm solar radio flux, Average Photospheric Magnetic Flux, interplanetary magnetic field (B z ) and the geomagnetic activity index A p during the ascending phase of the current solar cycle 24. We use both Lomb-Scargle periodogram and wavelet analysis technique and find evidence for a multitude of quasi-periodic oscillations in all the data sets. In high frequency range (10 days to 100 days), both methods yield similar significance periodicities around 20–35 days and 45–60 days in all data sets. In the case of intermediate range, the significant periods were around 100–130 days, 140–170 days and 180–240 days The Morlet wavelet power spectrum shows that all of the above-mentioned periods are intermittent in nature. We find that the well-known “Rieger period” of (150–160 days) and near Rieger periods (130–190 days) were significant in both solar, interplanetary magnetic field and geomagnetic activity data sets during cycle 24. The geomagnetic activity is the result of the solar wind-magnetosphere interaction. Thus the variations in the detected periodicity in variety of solar, interplanetary and geomagnetic indices could be helpful to improve our knowledge of the inter-relationship between various processes in the Sun-Earth-Heliosphere system.
KeywordsSun: activities Sun: magnetic field Sun: sunspots Sun: geomagnetic activities Sun: periodicities
This work utilizes SOLIS data obtained by the NSO Integrated Synoptic Program (NISP), managed by the National Solar Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under a cooperative agreement with the National Science Foundation. Wavelet software provided by C. Torrence and G. Compo is also gratefully acknowledged.
This work was supported by the BK21 plus program through the National Research Foundation (NRF) funded by the Ministry of Education of Korea.
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