Magnethydrodynamics is the subject of a web site at http://mysite.du.edu/~jcalvert/phys/mhd.htm which it is claimed is ‘closely related’ to plasma dynamics. It involves the dynamics of matter moving in an electromagnetic field, especially where currents established in the matter by induction modify the field. It involves conducting fluids, liquid and gas, but differs from plasma dynamics. Go to the web site and read online or download the Introduction and following article which has the mathematics in 12 pages of text and diagrams. See what you think. See especially what he thinks sun spots are and what they do. For example, and to wet your whistle, he likens sun spots to evidence of the solar magnetic field – magnetic flux entering or leaving the Sun vertically in which the field magnitude can be thousands of gauss. Sun spots occur in pairs of opposite polarity at roughly the same latitude. Polarities of the leading and following sun spots are reversed in the opposite hemisphere and polarities reverse in earch successive 11 year cycle. The cycle is really of 22 years with two maxima in each cycle. Sun spots do not occur in polar or equatorial regions of the Sun he claims, they are restricted to mid latitudes.