Worldwide features of the strength of recurrent geomagnetic activity

Rangarajan, G. K. ; Bhattacharyya, A. (1983) Worldwide features of the strength of recurrent geomagnetic activity Proceedings of the Indian Academy of Sciences - Earth and Planetary Sciences, 92 (1). pp. 5-13. ISSN 0253-4126

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Variation of the strength of recurrent geomagnetic activity, which occurs just before a sunspot minimum, with local time is studied for a network of observatories covering different latitude and longitude zones. For this purpose, hourly averages of horizontal intensity(H) for each UT hour for 173 days, which are totally free of disturbances due to solar transients, have been subjected to spectral analysis. Well-defined spectral peaks associated with periodicities of 28, 14 and 9 days were present in almost all the spectra. The pattern of daily variation of the strength of the 27-day signal changes from a diurnal one at low latitudes to a semi-diurnal one near the Sq focus and in this region, the 14-day signal appears to have an independent origin irrespective of the longitude zone. A study of 27-day oscillation in mean dailyH field also indicates that apart from ring current modulation, both Sq and electrojet fields also undergo 27-day oscillations during the declining phase of a solar cycle possibly through the ionospheric wind system.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Worldwide Features; Geomagnetic Activity; Sunspot Minimum; Ring Current; Tidal Winds
ID Code:29076
Deposited On:18 Dec 2010 05:38
Last Modified:17 May 2016 12:03

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