The Sun's Dynamo: Standard Model, Prediction Methods, + New Ideas
The puzzle of the Sun's dynamo has been regarded as one of the main unsolved
problems in physics. Enumerated by no less a personage than Albert Einstein,
it still remains a great unsolved problem. This is easily illustrated by
predictions of what the current solar cycle, #24, will do. Much controversy
exists in both the methods and manner of predicting the size of the upcoming
solar cycle. Solar physicists cannot even agree as to where the solar dynamo
is located! Except that it is inside the Sun!
There is a kind of "Where's Waldo?",or "Where's Osama?" question involved. We are gradually learning where the dynamo is NOT, but we still can't pin down where it is. So, progress resembles a kind of "trench warfare," gradually pushing back where the magnetism is NOT, and "whatever else remains," as Sherlock Holmes would say, "however improbable must be the truth." With this view in mind, we focus on the bottom of the Sun's convection zone, traditionally, and also discuss a novel idea, the top of the convection zone. The first has become the standard solar dynamo: a "deep mean field dynamo," pioneered by Babcock, Leighton, and Parker. It has many attractive features, explaining the so-called "butterfly diagram", Hale's 22 year magnetic cycle and his laws of polarity, etc. As an outgrowth, we developed a powerful tool 3 1/2 decades ago, used by NASA for predicting solar activity. It helps plan satellite orbits which are affected by the Sun's EUV (and helped plan the successful Hubble refurbishing mission). Proved successful now for 3 solar cycles, and seemingly now for a 4th, should the current cycle maintain its low profile, the general workings of the solar dynamo are still mysterious. We end with a glimpse of novel ideas on the dynamo: a shallow Babcock-Leighton model, using the new mathematical tools of "percolation" and "cellular automata."