The Transparency of Solar Coronal Active Regions

摘要: Resonance scattering has often been invoked to explain the disagreement between observed and predicted line ratios of Fe XVII λ15.01 λ15.26 (the "3C/3D" ratio). In this process photons λ15.01, with its much higher oscillator strength, are preferentially scattered out sight, thus reducing ratio. Recent laboratory measurements, however, have found significant inner-shell XVI lines at 15.21 15.26 A, suggesting that 3C/3D ratio results from blending. Given our new understanding fundamental spectroscopy, we reexamined original solar spectra, identifying λ15.21 measuring flux account for contribution flux. Deblending brings into good agreement experimental ratio; hence, find no need invoke resonance scattering. Low opacity in also implies low XV λ284.2, ruling as cause fuzziness TRACE SOHO-EIT 284 A images. The images must, instead, be unresolved due large number structures temperature. Insignificant future instruments spatial resolution could resolve active region plasma component loop structures.