Solar X-ray and EUV corona and their relation to the magnetic activity

We have studied the solar magnetic cycle in corona using X-ray data from YOHKOH and Extreme Ultraviolet data from SOHO/EIT. Soft X-ray data last the period from after the maximum cycle 22 to the maximum cycle 23 (1991-2001). The SOHO/EIT Extreme Ultraviolet data are used for the period from 1996 to 2003. These data provide us a unique opportunity to look at the solar corona on the solar disc and to compare with the magnetic activity, directly. Our studies reveal a close relationship between the coronal emissions and the photospheric magnetic field in the axisymmetrical case. The evolution of coronal structures in X-ray and EUV can be considered as a proxy of the coronal magnetic field and demonstrates a development of the solar magnetic cycle in corona. It is shown that the most important feature of the coronal cycle is the forming of giant loops structure visible in X-ray and, partially, in EUV (284A) on the solar disk. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.