PREDNASAJUCI / LECTURER :

Vojto Rusin

NAZOV / TITLE :

The solar corona ellipticity and magnetic fieds of the Sun

ABSTRAKT / ABSTRACT :

In this presentation, we will focus on the shape of the white-light corona
as obtained during total solar eclipse observations, which changes with the phase
of the solar activity cycle. One of the parameters of such research is an index,
which Ludendorff introduced in the 1930s and is based on the photometry of the white-light
corona (isophotes) and the isophotes flattening determined from them. It is called
the photometric flattening index, or Ludendorff index, and, although its calculation is very simple,
the differences for the same eclipses are quite different. While the value of polar magnetic field
strengths has dropped out  in the last three cycles of solar activity twice,
the value of the index has not changed. We will also present its values for the
last 150 years, which are approximately the same for a given phase of the cycle, but the solar
activity of the Sun, expressed by the Wolf number, is quite different for each cycle.
The white-light corona arises  by the scattering of solar radiation on free electrons
in the corona and its structures are built up by solar magnetic fields.