The coronal hole at the 7 March 1970 solar eclipse

Abstract

In 1957, the author has described the morphology of the monochromatic corona, using synoptic charts of the green line intensity. He drew attention to regions of very low emission that could be identified on several consecutive rotations. For these features, he coined the term ‘Locher’ what means ‘holes’. Such a hole appeared in the SW-quadrant of the Sun at the total eclipse of March 7, 1970. From the photometry in white light, the density distribution in the hole has been calculated under the assumption of a circular cross section. The result is presented in Figure 2. In the central part, whose diameter is roughly half that of the whole hole, the density is less than 10% of the density of the undisturbed corona at the same distance from the Sun. The hole did appear in a region free of solar activity for three consecutive rotations (Figure 3).