Connection between solar activity cycles and grand minima generation

Abstract

Aims. The revised dataset of sunspot and group numbers (released by WDC-SILSO) and the sunspot number reconstruction based on dendrochronologically dated radiocarbon concentrations have been analyzed to provide a deeper characterization of the solar activity main periodicities and to investigate the role of the Gleissberg and Suess cycles in the grand minima occurrence. Methods. Empirical mode decomposition (EMD) has been used to isolate the time behavior of the different solar activity periodicities. A general consistency among the results from all the analyzed datasets verifies the reliability of the EMD approach.Results. The analysis on the revised sunspot data indicates that the highest energy content is associated with the Schwabe cycle. In correspondence with the grand minima (Maunder and Dalton), the frequency of this cycle changes to longer timescales of ∼14 yr. The Gleissberg and Suess cycles, with timescales of 60−120 yr and ∼200−300 yr, respectively, represent the most energetic contribution to sunspot number reconstruction records and are both found to be characterized by multiple scales of oscillation. The grand minima generation and the origin of the two expected distinct types of grand minima, Maunder and longer Spörer-like, are naturally explained through the EMD approach. We found that the grand minima sequence is produced by the coupling between Gleissberg and Suess cycles, the latter being responsible for the most intense and longest Spörer-like minima (with typical duration longer than 80 yr). Finally, we identified a non-solar component, characterized by a very long scale oscillation of ∼7000 yr, and the Hallstatt cycle (∼2000 yr), likely due to the solar activity. Conclusions. These results provide new observational constraints on the properties of the solar cycle periodicities, the grand minima generation, and thus the long-term behavior of the solar dynamo.

Multifractal and Chaotic Properties of Solar Wind at MHD and Kinetic Domains: An Empirical Mode Decomposition Approach

“…Through the Hilbert Transform (HT), which is a linear mathematical operator that takes each IMF and produces a function by convolution with the function , each empirical mode can be written as modulated both in amplitude and in frequency where and are the instantaneous amplitude and frequency of the k -th empirical mode, respectively, and ℜ is the real part of the exponential. The HT allows to investigate non-stationary features of the time series, being a function of time, and also its nonlinear behavior, due to the time-dependence of (e.g., [ 43 , 51 ]). Derived from both and , the instantaneous local energy content is studied by contouring the squared-amplitude in a time-frequency plane, i.e., by defining the so-called Hilbert-Huang spectrum [ 43 ].…”

Timescale separation in the solar wind‐magnetosphere coupling during St. Patrick's Day storms in 2013 and 2015

“…An alternative method to unveil the characteristic timescales of nonstationary signals is the empirical mode decomposition (EMD) technique, introduced by Huang et al [] [see also Wu and Huang , ], as a preconditioning method for the application of the Hilbert transform. EMD is an adaptive method based on the local characteristics of the data, useful to analyze natural signals [ Vecchio et al , , , ; Alberti et al , ; Vecchio et al , ], also including geomagnetic time series [ De Michelis et al , ; De Michelis and Consolini , ]. Particularly, the EMD does not require to have any “a priori” assumption on the functional form of the basis of the decomposition.…”

Reply to comment on the paper “ on a role of quadruple component of magnetic field in defining solar activity in grand cycles” by Usoskin (2017)

“…For example, the Gleissberg cycle is not a single 100-yr mode but rather a wide-band variability with typically two sub-modes, 70-90 years and 120-150 years (e.g. Ogurtsov et al, 2002;Vecchio et al, 2017).…”