Active Longitudinal Structures of the Sun from MDI and EIT Observations

Abstract

We present results of investigation of the large-scale structure of the solar corona during the transition period between solar cycles 22 and 23 and at the beginning of the current cycle 23 using the SOHO/EIT EUV data obtained in 171 Å, 195 Å, 284 Å and 304 Å lines. For this analysis the data were transformed into synoptic maps for each of the spectral lines, and for the 195/171 line ratio which is an index of the coronal temperature. The synoptic maps reveal stable longitudinal structures in the coronal intensities and temperature, which are related to large-scale magnetic field structures. We discuss the relation between the coronal and photospheric magnetic structures obtained from the SOHO/MDI data, and compare the rotation rates of these structures with the rotation profile of the solar interior in order to determine the possible origin of the coronal structures.