A USER'S GUIDE TO UVCS/SOHO

Section 1
Introduction


* What Does UVCS Measure?

The purpose of the UVCS mission is to provide a detailed description of the extended solar corona that can be used to address a broad range of scientific questions regarding the nature of the solar corona and the generation of the solar wind.

UVCS makes measurements of the solar corona between 1.3 and 12 solar radii from sun center with high spectral and spatial resolution. The instrument creates an artificial solar eclipse in ultraviolet light, blocking out the bright light from the solar disk and allowing observation of the less intense (by several orders of magnitude) light from the extended corona. The corona emits most of its ultraviolet intensity in spectral emission lines, and the shapes and strengths of these lines contain valuable information about the microscopic and macroscopic behavior of the highly-ionized coronal plasma. From the spectroscopic measurements at ultraviolet wavelengths, the

can be determined. Information about the

can also be learned. UVCS has observed about 37 spectral lines in the extended solar corona for H I and ions of C, N, O, Mg, Al, Si, S, Fe, and Ni.


* Spectral Lines

Plotted below are preliminary identifications for observed spectral lines in the LYA (H I Lyman alpha) and O VI Channels, observed in active-region streamers on the East limb of the Sun, on 23-24 July 1996, at a heliocentric distance of 1.5 solar radii (see Raymond et al. 1997).


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