Observed rotation of the solar corona and its relation to the data of helioseismology

Rotation pattern of the Sun represents a necessary condition for realization of the dynamo mechanism, mostly operating at the bottom of the convective zone (tachocline layer). We have studied the differentiality of rotation in the solar corona on the database of the Fe XIV 530.3 nm coronal green line brightness. Our own data, covering more than five solar cycles (1939-2001), has been subjected to the Spectral Variation Analysis (SVAN) and the following principal results were obtained: (a) The period of rotation increases from 27 days at the equator to a little more than 29 days at the latitudes of +/-40 degrees, displaying much slower differentiality than that for majority of the solar photospheric phenomena. (b) This differentiality diminishes at +/-40 latitudinal degrees and then the rotation displays practically rigid character (period of about 29.5 days) up to polar regions. (c) A more detailed analysis revealed that two quasi-rigid modes of coronal rotation probably exist, the faster one with period of 27 days (slightly increasing towards the higher latitudes), and the slow one displaying the rotational period of about 30.5 days. These two modes seem to agree with the latest findings of helioseismology. The observed dependence of coronal rotation on the solar latitude apparently results from a combination of the two modes. (d) There is a trace that the temporal variations of the faster mode could indicate a presence of the torsional oscillations in the corona.