Living Reviews in Solar Physics: "Dynamo models of the solar cycle"
Charbonneau, P. Dynamo models of the solar cycle. Living Rev Sol Phys 17, 4 (2020). https://doi.org/10.1007/s41116-020-00025-6
Open Access | Review Article
Published: 17 June 2020
Major update of 2nd ed. (2010): https://doi.org/10.12942/lrsp-2010-3
This paper reviews recent advances and current debates in modeling the solar cycle as a hydromagnetic dynamo process. Emphasis is placed on (relatively) simple dynamo models that are nonetheless detailed enough to be comparable to solar cycle observations. After a brief overview of the dynamo problem and of key observational constraints, I begin by reviewing the various magnetic field regeneration mechanisms that have been proposed in the solar context. I move on to a presentation and critical discussion of extant solar cycle models based on these mechanisms, followed by a discussion of recent magnetohydrodynamical simulations of solar convection generating solar-like large-scale magnetic cycles. I then turn to the origin and consequences of fluctuations in these models and simulations, including amplitude and parity modulation, chaotic behavior, and intermittency. The paper concludes with a discussion of our current state of ignorance regarding various key questions relating to the explanatory framework offered by dynamo models of the solar cycle.
Solar cycle models based on the Babcock–Leighton mechanism have undergone major developments in the past decade, and this is reflected in a new section entirely devoted to this class of dynamo models. In addition, also in the past decade global magnetohydrodynamical simulations of solar convection and dynamo action have reached a level where they now can generate large-scale magnetic fields undergoing more or less solar-like regular magnetic polarity reversals. These simulations are now discussed in a new section, with emphasis placed on physical links with geometrically and dynamically simpler dynamo models. The section on amplitude fluctuations and Grand Minima has been shortened and reworked to emphasize generic behaviors, with pointers to the technical literature for illustrative examples. About 130 references have been added.
Paul Charbonneau is a professor in the astrophysics group of the physics department of the University of Montréal. He has been working on solar activity and its possible influence on the Earth climate. At Springer, he has also published the book "Solar and Stellar Dynamos: Saas-Fee Advanced Course 39" (2013). His Living Review on "Dynamo models of the solar cycle" is now in its 3rd edition (2005, 2010, 2020).