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E. E. Benevolenskaya (Stanford University)
Six years of EIT/SOHO data in four EUV lines (1996-2001) and ten years of soft X-ray YOHKOH data (1991-2001) are analyzed in the form of coronal synoptic maps for the investigation of solar cycle variations of the corona. The evolution of coronal structures is closely related to sunspot activity, photospheric magnetic field, and topology of the large-scale magnetic field. The coronal structures visible in extreme ultraviolet and soft X-ray as extended bright loops reflect the non-axisymmetrical magnetic structure of the Sun changing with solar cycle. The long-living coronal structures are related to complexes of solar activity and display the quasiperiodic behavior ('impulses' of coronal activity) with periods of 1.0-1.5 year in the axisymmetrical distribution of EUV and X-ray fluxes during the current cycle. There is a close correlation between the soft X-ray intensity and photospheric magnetic flux in mid-latitudinal zones, which can be represented by the power law. The power index is higher for the period of the declining phase and minimum of solar activity than for its rising phase and maximum. This indicates that coronal heating may have different characteristics at different phases of the solar cycle, and depends not only on the magnetic flux, but probably also on structural properties of the magnetic field.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.