Large-scale Solar Coronal Structures in Soft X-rays and Their Relationship to the Magnetic Flux

We have investigated the relationship between magnetic activity and coronal structures using soft X-ray data from the Yohkoh soft X-ray telescope and magnetic field data from the Kitt Peak Solar Observatory for the period of 1991–2001 and EUV data from the Solar and Heliospheric Observatory EUV Imaging Telescope for 1996–2001. The data are reduced to Carrington synoptic maps, which reveal two types of migrating structures of coronal activity at low and high latitudes in the time-latitudinal distribution. The low-latitude coronal structures, migrating equatorward, correspond to photospheric sunspot activity, and the high-latitude structures migrating toward the poles reflect polar activity of the Sun. We present the following new results: 1. The migrating high-latitude coronal magnetic structures are revealed in the soft X-ray data as complete bright giant loops connecting the magnetic field of the following part of active regions with the polar field. They appear during the rising phase and maximum of the solar cycle and show quasi-periodic impulsive variations with a 1–1.5 yr period. 2. The soft X-ray intensity of these loops has a strong power-law correlation with the photospheric magnetic flux. The power-law index, which on average is close to 2, shows variations with the solar cycle: it is higher for the period of the declining phase and minimum of solar activity than for the rising phase and maximum. Subject headings: Sun: activity — Sun: corona — Sun: magnetic fields — Sun: UV radiation — Sun: X-rays, gamma rays