On solar cycle predictions and reconstructions

Abstract

Context. Generally, there are two procedures for solar cycle predictions: the empirical methods -statistical methods based on extrapolations and precursor methods -and methods based on dynamo models. Aims. The goal of the present analysis is to forecast the strength and epochs of the next solar cycle, to investigate proxies for grand solar minima and to reconstruct the relative sunspot number in the Maunder minimum. Methods. We calculate the asymmetry of the ascending and descending solar cycle phases (Method 1) and use this parameter as a proxy for solar activity on longer time scales. Further, we correlate the relative sunspot numbers in the epochs of solar activity minima and maxima (Method 2) and estimate the parameters of an autoregressive moving average model (ARMA, Method 3). Finally, the power spectrum of data obtained with the Method 1 is analysed and the Methods 1 and 3 are combined. Results. Signatures of the Maunder, Dalton and Gleissberg minima were found with Method 1. A period of about 70 years, somewhat shorter than the Gleissberg period was identified in the asymmetry data. The maximal smoothed monthly sunspot number during the Maunder minimum was reconstructed and found to be in the range 0-35 (Method 1). The estimated Wolf number (also called the relative sunspot number) of the next solar maximum is in the range 88-102 (Method 2). Method 3 predicts the next solar maximum between 2011 and 2012 and the next solar minimum for 2017. Also, it forecasts the relative sunspot number in the next maximum to be 90 ± 27. A combination of the Methods 1 and 3 gives for the next solar maximum relative sunspot numbers between 78 and 99. Conclusions. The asymmetry parameter provided by Method 1 is a good proxy for solar activity in the past, also in the periods for which no relative sunspot numbers are available. Our prediction for the next solar cycle No. 24 is that it will be weaker than the last cycle, No. 23. This prediction is based on various independent methods.

Meridional motions and Reynolds stress from SDO/AIA coronal bright points data

“…Hara (2009) analysed X-ray bright points observed by the Yohkoh soft X-ray telescope in the period 1994−1998. This time period starts close to the end of cycle 22 and ends soon after the beginning of cycle 23 (see Table 1 in Brajša et al 2009).…”

Solar and Stellar Dynamos

“…Is it a purely stochastic effect, or is it an example of deterministic chaos? Economists have long regarded the solar cycle as an example of stochastic behaviour, and Barnes, Sargent & Tryon (1980) showed that an Autoregressive Moving Average (ARMA) model (constructed by combining a three-term recurrence relation with filtered Gaussian noise) provided a very plausible representation of solar activity (see also Brajsa et al 2009). If we seek a more causal description, we may suppose that the cyclic dynamo is disturbed by fluctuations in the underlying hydrodynamics of the convection zone, which we can regard as random.…”

A new method for forecasting the solar cycle descent time

“…While some methods provide predictions well in advance or close to the time of initiation of an upcoming SC, a few other methods offer step-by-step predictions as an SC advances. It has been shown that precursor methods show better performance compared with other prediction methods (Li et al 2001;Brajsa et al 2009). Some of the aforementioned methods are based on a physical approach (Dikpati & Charbonneau 1999;Schatten 2005;Dikpati et al 2006;Dikpati & Gilman 2008;Svalgaard et al 2005) rather than a strictly numerical approach.…”