First Results from the Soho Ultraviolet Coronagraph Spectrometer

• Published in: Solar physics Vol. 175; no. 2; pp. 613 - 644
• Main Authors: Kohl, J L, Noci, G, Antonucci, E, Tondello, G, Huber, M C; E, Gardner, L D, Nicolosi, P, Strachan, L, Fineschi, S, Raymond, J C, Romoli, M, Spadaro, D, Panasyuk, A, Siegmund, O H; W, Benna, C, Ciaravella, A, Cranmer, S R, Giordano, S, Karovska, M, Martin, R, Michels, J, Modigliani, A, Naletto, G, Pernechele, C, Poletto, G, Smith, P L
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.10.1997
• Subjects: Corona; Solar physics; Studies; Velocity distribution
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1023/A:1004903206467

The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used to observe the extended solar corona from 1.25 to 10 R from Sun center. Initial observations of polar coronal holes and equatorial streamers are described. The observations include measurements of spectral line profiles for HI Lα and Lβ, Ovi 1032 Å and 1037 Å, Mgx 625 Å, Fexii 1242 Å and several others. Intensities for Mgx 610 Å, Sixii 499 Å, and 520 Å, Sx 1196 Å, and 22 others have been observed. Preliminary results for derived H^sup 0^, O^sup 5+^, Mg^sub 9+^, and Fe^sup 11+^ velocity distributions and initial indications of outflow velocities for O^sup 5+^ are described. In streamers, the H^sup 0^ velocity distribution along the line of sight (specified by the value at e^sup -1^, along the line of sight) decreases from a maximum value of about 180 km s^sup -1^ at 2 R to about 140 km s^sup -1^ at 8 R. The value for O^sup 5+^ increases with height reaching a value of 150 km s^sup -1^ at 4.7 R. In polar coronal holes, the O^sup 5+^ velocity at e^sup -1^ is about equal to that of H^sup 0^ at 1.7 R and significantly larger at 2.1 R. The O^sup 5+^ in both streamers and coronal holes were found to have anisotropic velocity distributions with the smaller values in the radial direction.[PUBLICATION ABSTRACT]