Relationship between the coronal shape and the magnetic field topology during the solar cycle

Abstract

We have observed ten solar eclipses during the 1973–1999 period, three of them being recorded during the rising phase of the present solar cycle 23. The observed shapes of the white-light corona are confronted with the magnetic field topology, as calculated for the corresponding eclipse days. A close relationship of the distinctive large-scale coronal structures (coronal streamers, coronal holes, polar plumes, etc.) with the calculated magnetic field structures and with the actual position of the heliospheric current sheet (as derived for the source surface at r = 2.5 R ⊙) is evident. The found relations suggest a new understanding of the coronal shape evolution during the solar cycle. It is shown that “the isogausses” and the coronal isophotes create two systems of mutually orthogonal curves. The nature of this finding is also well confirmed by estimating of the magnetic field strength inside the coronal holes observed during “our” eclipses.