Information Theoretic Approach to Discovering Causalities in the Solar Cycle

Document Type

Article

Publication Date

2-15-2018

Keywords

Dynamo; Sun: Faculae, plages; Sun: sunspots; Sun: activity; Sun: magnetic fields; Sun: evolution; Sun: fundamental parameters; Methods: statistical

Abstract

The causal parameters and response lag times of the solar cycle dynamics are investigated with transfer entropy, which can determine the amount of information transfer from one variable to another. The causal dependency of the solar cycle parameters is bidirectional. The transfer of information from the solar polar field to the sunspot number (SSN) peaks at lag time (τ) ~ 30–40 months, but thereafter it remains at a persistently low level for at least 400 months (~3 solar cycles) for the period 1906–2014. The latter may lend support to the idea that the polar fields from the last three or more solar cycles can affect the production of the SSN of the subsequent cycle. There is also a similarly long-term information transfer from the SSN to the polar field. Both the meridional flow speed and flux emergence (proxied by the SSN) transfer information to the polar field, but one transfers more information than the other, depending on the lag times. The meridional flow speed transfers more information than the SSN to the polar field at τ ~ 28–30 months and at τ ~ 90–110 months, which may be consistent with some flux transfer dynamo models and some surface flux transport models. However, the flux emergence transfers more information than the meridional flow to the polar field at τ ~ 60–80 months, which may be consistent with a recently developed surface flux transport model. The transfer of information from the meridional flow to the SSN peaks at τ ~ 110–120 months (~1 solar cycle).

Journal Title

The Astrophysical Journal

Volume

854

Issue

2

First Page

85

DOI

https://doi.org/10.3847/1538-4357/aaa8e7

First Department

Engineering

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