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Journal Articles SOLAR PHYSICS Year : 2017

Identification of Gleissberg Cycles and a Rising Trend in a 315-Year-Long Series of Sunspot Numbers

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Abstract

We show in this short note that the method of singular spectrum analysis (SSA) is able to clearly extract a strong, clean, and clear component from the longest available sunspot (International Sunspot Number, ISN) time series (1700 - 2015) that cannot be an artifact of the method and that can be safely identified as the Gleissberg cycle. This is not a small component, as it accounts for 13% of the total variance of the total original signal. Almost three and a half clear Gleissberg cycles are identified in the sunspot number series. Four extended solar minima (XSM) are determined by SSA, the latest around 2000 (Cycle 23/24 minimum). Several authors have argued in favor of a double-peaked structure for the Gleissberg cycle, with one peak between 55 and 59 years and another between 88 and 97 years. We find no evidence of the former: solar activity contains an important component that has undergone clear oscillations of ≈90 years over the past three centuries, with some small but systematic longer-term evolution of "instantaneous" period and amplitude. Half of the variance of solar activity on these time scales can be satisfactorily reproduced as the sum of a monotonous multi-secular increase, a ≈90-year Gleissberg cycle, and a double-peaked (≈10.0 and 11.0 years) Schwabe cycle (the sum amounts to 46% of the total variance of the signal). The Gleissberg-cycle component definitely needs to be addressed when attempting to build dynamo models of solar activity. The first SSA component offers evidence of an increasing long-term trend in sunspot numbers, which is compatible with the existence of the modern grand maximum.
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insu-03748865 , version 1 (10-08-2022)

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Jean-Louis Le Mouël, Fernand Lopes, Vincent Courtillot. Identification of Gleissberg Cycles and a Rising Trend in a 315-Year-Long Series of Sunspot Numbers. SOLAR PHYSICS, 2017, 292, ⟨10.1007/s11207-017-1067-6⟩. ⟨insu-03748865⟩
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