Rotation of the coronal magnetic field

Abstract

The coronal magnetic field rotates differently than the photosphere. The field configuration of the corona can be modeled using the observed photospheric field and a potential field model. Correlation of the field patterns at different latitudes with a lag near one solar rotation shows much less differential rotation than observed in the photospheric field; however, the peak is very broad and determines the rotation rather poorly. Consideration of longer lags reveals a more complex rotational structure and indicates different rotation rates in the northern and southern hemispheres. Spectral analysis of the equatorial dipole component of the coronal field reveals an organization into just a few discrete rotation frequencies which are apparently present simultaneously. Spectral analysis of the field at different latitudes shows that the frequencies are present simultaneously but in different hemispheres. During solar cycle day period, while the northern hemisphere rotates faster,