Forecasting geomagnetic activity at monthly and annual horizons: Time series models

Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> 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.…”

“…Geomagnetic activity forecast has been over the order of hours or days (McPherron, 1999;Abunina et al, 2013). The annual or monthly prediction of geomagnetic activity is within a limited accuracy (over 20 %) due to irregular variation in the time series (McPherron, 1999;Gordon, 2015). In the earlier years, Kane (1988) even pointed out that it is impossible to forecast long-term geomagnetic activity through analyzing the time series of the Ap and aa index (refer also to Gordon, 2015).…”

“…The annual or monthly prediction of geomagnetic activity is within a limited accuracy (over 20 %) due to irregular variation in the time series (McPherron, 1999;Gordon, 2015). In the earlier years, Kane (1988) even pointed out that it is impossible to forecast long-term geomagnetic activity through analyzing the time series of the Ap and aa index (refer also to Gordon, 2015). Geomagnetic activity near the solar minimum or at the decreasing phase of the solar cycle has been widely used to predict the maximum amplitude of the sunspot cycle but was seldom used to predict the maximum amplitude of the geomagnetic activity itself.…”

“…In the earlier years, Kane (1988) pointed out that it is impossible to forecast long-term geomagnetic activity through analyzing the daily, monthly, and annual Ap and aa indices. Gordon (2015) demonstrated that long-term geomagnetic activity can only be predicted to within a limited threshold of accuracy due to the irregular trends and cycles in the annual data and nonlinear variability in the monthly series, through analyzing the aa index.…”