High-resolution images of the sun in the soft x-ray to extreme ultraviolet(EUV) regime have been obtained with normal-incidence Cassegrain multilayer telescopes operated from a sounding rocket in space. The inherent energy-selective property of multilayer-coated optics allowed distinct groups of emission lines to be isolated in the solar corona and the transition region. The Cassegrain telescopes provided images in bands centered at 173 and 256 angstroms. The bandpass centered at 173 angstroms is dominated by emission from the ions Fe IX Fe X. This emission is from coronal plasma in the temperature range 0.8 x 10(6) to 1.4 x 10(6)K. The images have angular resolution of about 1.0 to 1.5 arc seconds, and show no degradation because of x-ray scattering. Many features of coronal structure, including magnetically confined loops of hot plasma, coronal plumes, polar coronal holes, faint structures on the size scale of supergranulation and smaller, and features due to overlying cool prominences are visible in the images. The density structure of polar plumes, which are thought to contribute to the solar wind, has been derived from the observations out to 1.7 solar radii.
We have obtained high resolution ( -1 arcsec) X-ray and EUV images of the solar corona with two rocket-borne normal incidence Cassegrain multilayer telescopes. The Cassegrain images correspond to material at -1 000 000 K (2 -173A) and -80000K (A -256A). Other images, at somewhat lower resolution, were obtained with Herschelian multilayer telescopes and Wolter-Schwarzschild hybrid grazing incidence/multilayer optical systems. We discuss the Cassegrain and Herschelian images, emphasizing the analysis of polar plumes observed at the limb of the Sun. Polar plumes are thought to represent structures that contribute signifiLantly to the flow of coronal material into the solar wind. We will also comment briefly on other coronal features observed, including coronal holes, the chromospheric network, active region loops, and prominence cavities. Multilayer technology represents a major breakthrough in astronomical X-ray and EUV imaging; we will discuss the application of specific multilayer techniques to astronomical observations, emphasizing observations of the sun. We will also report on current efforts in our laboratories to develop a comprehensive Multi-Spectral Solar Telescope Array rocket instrument for the study of a wide variety of problems related to the solar atmosphere.
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