Three-dimensional structures of magnetostatic atmospheres. IV - Magnetic structures over a solar active region

A static model is presented for the long-lived structures over a solar active region dominated by a pair of sunspots of opposite magnetic polarities. The magnetic field is approximately force-free high in the atmosphere but interacts strongly with the plasma and gravity in the lower region through cross-field electric currents. Basic atmospheric features long discussed in the literature can be reproduced in realistic geometry, such as the density depletion over a sunspot, magnetic shear, and levitated magnetic flux ropes interpretable as chromospheric filaments. Explicit solutions showing these features are described and compared, with a discussion of the implications for the interpretation of vector-magnetograph data. These solutions are illustrative examples taken from a large set obtainable by transforming the magnetostatic equations to solvable, linear differential equations given in the preceding paper in this series.