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J. Zhang, M.R. Kundu, S.W. White (U. of Maryland)
The Sun's Corona, which is composed of a few million degree plasma, can be best viewed in two electro-magnetic wavelength domains, one from a few Angstrom to hundreds of Angstrom (in Soft X-ray and EUV domains), the other from a few centimeter to several tens of centimeter wavelengths (in radio domain). In this paper, we present the detailed and quantitative comparison of corona observations made in these two domains with high spatial resolution and full view of the Sun. The EUV observations were taken with EIT (Extreme Ultraviolet Imager) on board SOHO (Solar and Heliospheric Observatory) in Fe spectral lines centered at 171, 195 and 284 Angstrom, respectively; while the radio observations were taken with the VLA (Very Large Array) at 6 and 20 cm, and NRH (Nobeyama Radio Heliograph) at 1.8 cm (17 Ghz), respectively. We have found that there exists excellent morphological similarity of corona features between these two sets of observations. However, the quantitative comparisons have revealed that the predicted radio flux from EUV observations based on traditional assumptions is always higher than that observed directly by radio instruments, by a factor of 4 to 6. The discrepancy is probably due to the underestimation of coronal ion abundance (e.g. Meyer's abundance) by a factor of 4 to 6.
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