Fine structure of solar magnetic fields.

Extension of the deduction of magnetic fields from chromospheric structure to active regions and transverse fields. Fields independently predicted by these rules from a high-resolution H alpha filtergram are compared with a high-resolution magnetogram. The H alpha method has the advantage over conventional magnetograms that it shows transverse fields and relates the fields to the real sun. It has the disadvantage that higher spatial resolution is required and that it is difficult and time consuming in very complicated regions. The response of the chromosphere to magnetic fields is most consistent. Vertical field is invariably marked by bright plage, with brightness roughly proportional to the field strength (except for sunspots). All dark fibrils mark transverse fields and are parallel to field lines. All polarity changes are marked by dark fibrils, which may be transverse fibrils perpendicular to the field boundary, or filaments (prominences) which connect more distant points, and in which the field lines run nearly parallel to the boundary. The asymmetry between preceding and following polarity found by Veeder and Zirin (1970) does not exist; it was due to the low resolution of the Mount Wilson magnetograms.