THERMAL AND DENSITY STRUCTURE OF POLAR PLUMES .1. ANALYSIS OF EUV OBSERVATIONS WITH A MULTILAYER CASSEGRAIN TELESCOPE

Normal incidence multilayer coated EUV/XUV optical systems provide a p owerful technique for the study of the structure of the solar corona. Such systems permit the imaging of the full solar disk and corona with high angular resolution in narrow wavelength bands that are dominated by a single line or a line multiplet excited over a well defined rang e of temperatures. We have photometrically analysed, and derived tempe rature and density information from, images of polar plumes obtained w ith a multilayer Cassegrain telescope operating in the wavelength inte rval lambda = 171 to 175 Angstrom, which is dominated by FeIx and Fex emission. This observation was obtained in October 1987, and is the fi rst high resolution observation of an astronomical object obtained wit h normal incidence multilayer optics techniques. We find that photomet ric data taken from this observation, applied to a simple, semi-empiri cal model of supersonic solar wind flow, are consistent with the idea that polar plumes are a source of the solar wind. However, we are not able to uniquely trace high speed streams to polar plumes. The tempera tures that we observed are typically similar to 1500 000 K for both th e plumes and the interplume regions, with the plume temperatures sligh tly higher than those of the surrounding atmosphere. Typical electron densities of the plume and interplume regions,respectively, are 5 x 10 (9) cm(-3) and 1 x 10(8) cm(-3) at the limb of the Sun.