CONDITIONS FOR THE APPEARANCE OF BALD PATCHES AT THE SOLAR SURFACE

A general criterion for the existence of sections of the photospheric polarity inversion line where the overlying magnetic field lines are p arallel to the photosphere is presented. It is shown that such section s, called ''bald patches'', exist for a wide range of parameters in po tential and constant-alpha force-free fields created by four concentra ted sources of magnetic flux. Bald patches appear when the polarity in version line is bent too much in an S-like manner. The appearance of b ald patches may be important for the formation of prominences and poss ibly for solar flares.