Quasi-biennial periodicities and heliospheric modulation of geomagnetic activity during solar cycles 22–24

Abstract

We have studied the monthly variations of geomagnetic activity (aa index) for the period 1986–2016. We have observed the heliospheric effect on geomagnetic activity, with zero time lag in the ascending and descending phases during the solar cycles 22 to 24. We have investigated midterm periodicity patterns of geomagnetic activity such as Rieger type (∼120–195d), quasi-annual period (∼378d), and quasi-biennial period (∼1.34–4.42y), using the fast Fourier transform technique and the Morlet wavelet transform for the period 1986–2016. We have investigated the amplitude of the sunspot number (SSN) for the next solar cycle 25 on the basis of the linear fit profile for maxima of SSNs due to minima of geomagnetic activity. Quasi-biennial oscillations (QBOs) represents the minimum amplitude in the period 1999–2000 and 2007–2013, and maximum in the ascending phase periods 1989, 1991, 2003, 2005 and 2015, i.e. QBOs of geomagnetic activity are strongly correlated with the monthly variation during solar cycles 22–24.

Estimating the maximum of the smoothed highest 3-hourly aa index in 3 d by the preceding minimum for the solar cycle

“…In addition, future solar activity is also unknown at the current time, and so it can not be directly used to estimate future geomagnetic activity. There are many methods that can be used to predict the maximum amplitude of the sunspot cycle (R m ), such as (i) statistical methods, employing the relationship between the inter-cycle parameters (Thompson, 1988;Hathaway et al, 1994) or the early rising rate (Thompson, 1988;Cameron and Schüssler, 2008;Du and Wang, 2012b); (ii) functional methods, using mathematical functions of a few parameters (Hathaway et al, 1994;Du, 2011d) for extrapolating the following monthly values; (iii) geomagnetic precursor methods (Brown and Williams, 1969;Ohl and Ohl, 1979;Du et al, 2009), using the geomagnetic activity near the solar minimum; and (iv) solar precursor methods (Schatten et al, 1978;Pesnell and Schatten, 2018), using the previous cycle's polar field.…”