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The Solar Clock
Author(s) -
Russell C.T.,
Jian L.K.,
Luhmann J.G.
Publication year - 2019
Publication title -
reviews of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 8.087
H-Index - 156
eISSN - 1944-9208
pISSN - 8755-1209
DOI - 10.1029/2019rg000645
Subject(s) - sunspot , solar dynamo , physics , dynamo , tachocline , solar cycle , helioseismology , convection zone , solar minimum , earth's magnetic field , magnetic flux , astrophysics , flux (metallurgy) , dynamo theory , atmospheric sciences , geophysics , convection , magnetic field , meteorology , solar wind , materials science , quantum mechanics , metallurgy
The Sun is powered by a very stable source of fusion energy in its core that radiates that energy outward in a constant flow. Yet it has a cycle of magnetic dynamo activity whose strength and duration are variable. This variability, which affects the Earth's “space climate,” points to temporal changes in the convective and diffusive transport of magnetic flux above the tachocline, where the flux is generated. The longest record we have of this variability is the time series of sunspot numbers. This record suggests that the interior of the Sun follows a clock‐like magnetic flux production cycle with a length of close to 11.05 years. The variations in sunspot cycle duration, as well as the sunspot number rise and fall times, their hemispheric asymmetries, and the maximum sunspot numbers of the individual cycles are likely produced in the process of the magnetic flux transport. Helioseismology continues to shed more light on the convection zone variabilities, including the “torsional oscillations” that seem to have a special connection to the emerging strong magnetic fluxes that produce the sunspots. These new observations may eventually lead to an explanation for the surprisingly good correlation between the rate of sunspot appearance and the maximum sunspot number and to a better understanding of the relationship between the solar dynamo and the sunspot number cycle. Better understanding of the polar regions awaits long‐term monitoring with a polar solar mission. Better predictions of near‐term space weather could be obtained from a permanent L5 monitor.