Comment on the paper by Popova et al. “On a role of quadruple component of magnetic field in defining solar activity in grand cycles”
Introduction
I was invited by a Guest Editor of the Topical Issue “Future solar activity” of JASTP journal to review the paper by Popova et al. (2017, denoted as P17 henceforth). Unfortunately, because of an unexpected technical problem with the publisher's online system, my review was lost during the manuscript processing and was not formally accounted for by the Editors when evaluating the P17 paper. However, it appears important to inform the scientific community about this review and, specifically, about scientific problems related to the P17 paper. This small Comment is written on the basis of the lost review and summarizes important flaws in the analysis method and results, published by P17.
Section snippets
The method
P17 aims to predict solar activity for 3000 year. The prediction method is based on a simple three-harmonic model of solar activity (two dipole and one quadruple components). The dipole components are periodic with frequencies being close to each other (21.41 and 22.62 years), which leads to a beating frequency of about 350–400 years. These dipole components were “defined” elsewhere (Zharkova et al., 2015) from a 35-year long set of solar data. However, as known from data processing,
Validation of the results
The result of the P17 paper factually voids the prediction by Zharkova et al. (2015) as appears obvious from Figs. 2 and 3 of P17, and the authors should have said clearly that their earlier results were not correct. However, even the new result disagrees with the available data for the last centuries. While the authors did not show a direct comparison between their results and other direct/indirect data on solar activity, I do it here in Fig. 1 for decadally averaged data (modulus of the final
Theoretical speculations
Theoretical speculations by P17 make little sense and are hardly relevant. The ad-hoc introduced quadruple component is vague. The authors wanted to add a third harmonic component to their model, but it is ungrounded why it should be a quadruple mode. The authors state that they are unable to find this mode in the real solar magnetic data and introduce it just out of the blue. Moreover, substituting the full dynamo equations with equations for “selected modes” is a dangerous exercise which can
Summary
Accordingly, as discussed above, the paper P17 contains several flaws which make the prediction of solar activity for the next thousands years unreliable.
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The method of P17 is based on an oversimplified and unreliable ad-hoc multi-harmonic representation of solar activity, and lacks quality control. In particular, the background solar dataset (35 years) does not allow determination of periodicities with sufficient accuracy to justify the beating period of 400 years. It is therefore impossible to
Acknowledgement
This work was made in the framework of ReSoLVE Centre of Excellence (Academy of Finland, project no. 272157).
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The Spörer minimum was deep
2019, Advances in Space ResearchCitation Excerpt :Extrapolation of the model to the past showed that the 15-16th centuries did not experience a solar minimum but was a period of high activity comparable to that in the 20th century (Popova et al., 2018, Zharkova et al., 2018). The findings of Popova et al. (2018), practically cancelling the SM, have been also seriously criticized (Usoskin, 2018). Considering the above controversy it seems rather useful to study solar activity during the Spoerer minimum in more detail.
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)
2018, Journal of Atmospheric and Solar-Terrestrial PhysicsCitation Excerpt :In this communication we provide answers to the comments by Dr. Usoskin (Usoskin, 2017, referred hereafter as U17) to our paper (Popova et al., 2017a, referred hereafter as PZSZ17).
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