Coronal holes with a saddle structure as deduced from Yohkoh observations

Saddle structures are seen in some images of the Sun in the soft X-rays obtained by Yohkoh mission. At the center of any such structure, there is a small coronal hole having the outlines of an astroid or a cross. The coronal saddles occur in magnetic configurations with a high degree of symmetry (quadrupoles). Comparison with the models shows that open field lines cannot be modeled using only the source surface.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1275–1279, October, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Grant No. 93-02-15112.