The relative intensities of CI lines in the solar EUV spectrum

✍ Scribed by Carole Jordan

• Publisher: Springer
• Year: 1967
• Tongue: English
• Weight: 447 KB
• Volume: 2
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00146492

✦ Synopsis

The relative intensity of two CI lines at 1993.6 • and 1657.4 A, observed in the limb spectrum of the sun, is a factor 2.6 • 10 a larger than that expected if both lines were optically thin. It is shown that the observed intensity ratio may be explained in terms of the transfer of photons from 2 1657.4 ~_ to it 1993.6/~ due to a large optical depth Jn the line at 1657.4/~. The observed upper limit on the relative intensity of two further lines at 1992.0 A and 1657.0/~ has been used to show that the line at 1993.6/~ is optically thin. Hence it is shown that z(1657.4 A) = 1300, and r(1993.6 A) = 0.44. These values provide an independent evaluation of optical depths against which chromospheric models may be checked. Assuming a mean temperature of Te = 8000 ~ and a mean scale height of 350 km, the optical depths lead to a mean hydrogen-particle density of N (H) = 1.4 • 101~ cm-8.