Solar dynamo
Key points
- Observations are cleared about the fact that there is some sort of dynamo operating inside the Sun. Theorists are not clear about how does this process actually works. There are different approaches/classes of models that are successfull to various extents to reproduce the observational facts. These approaches are completely disjunct: kinematic approaches, mean-field (averaged MHD) approaches, wave-like approaches. And more. That essentially means that our models attempt to reproduce the observational facts, but the very basic knowledge of the process itself is known only a little.
- Observational facts: 11-years cycle (from minimum to maximum and back to minimum). The real cycle is 22 years long (when also the polarity information about the magnetic field is taken into account) and consists of two 11-year subcycles. Empiracal laws. Spoerer law (migration of the activity belt towards the equator with the progression of the cycle), Joy's law (average tilt of active regions), Hale polarity laws (antisymmetry with respect to the equator, changes in polarity from cycle to cycle). Phase shift between the minimum and the reversal of the global magnetic field.
- Comic-book like Babcock model is very intuitive, but lacks a proper mathematical formulation. You should be able to explain the solar cycle using the Babcock model. Babcock-Leighton is a mathematical representation of the Babcock model (plus some other changes). Modern flux-transport dynamo is an extension to Babcock-Leighton model. So the modern dynamo somewhere deep down still contains the Babcock drawings!
- Want to read more? Read free Living Reviews in Solar Physics online and check the article about dynamo or solar-cycle predictions.