Coronal temperatures and temperature gradients from OSO-7 spectroheliograms

✍ Scribed by M. P. Nakada; R. D. Chapman; W. M. Neupert; R. J. Thomas

• Publisher: Springer
• Year: 1976
• Tongue: English
• Weight: 829 KB
• Volume: 47
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00154770

✦ Synopsis

Temperatures and temperature gradients for the outer corona are obtained from brightness gradients of EUV lines that were measured with the spectroheliograph on OSO-7. Brightness gradients show considerable deviations from isothermal model calculations that include collisional excitation and photoexcitation. A negative temperature gradient that gives both positive and negative ion abundance gradients appears to be able to account for the discrepancy. For ,~284 of Fexv, perhaps the strongest line from the outer corona, measurements during 1972 appear to be consistent with (i) a temperature near 2.3 x 106K near the equator at p = 1.3+0.1 solar radii from the solar center; (ii) (p/T) dT/dp values near -0.7 that extend from as low as p = 1.2 to about P = 1.8. Temperatures from strong lines of Fe xiv and Fe xv~ indicate that variations of about +0.2 x 106K exist along lines of sight where emission is appreciable. There appears to be some agreement between these results and temperature measurements from ion abundances in the solar wind and Doppler width of 3.5303.