qs097.foley01 Posted: 17-Jan-96 Updated: 12-Oct-96 Event specified: N/A
Carl Foley, Len Culhane and Loren Acton ABSTRACT. Images obtained with the Yohkoh Soft X-ray Telescope (SXT) have been used to obtain limb brightening profiles across the solar limb in the region of a northern polar coronal hole observed on the 3$^{rd}$ October 1992. The emission from the region was simulated using the results of the radiative equilibrium model fit to empirical data performed by Withbroe, 1988. The results demonstrate the consistency of the modelled temperatures and densities with the observation. A broadband filter ratio analysis is also performed on these data yielding line of sight average temperatures which vary from 1.35+-0.15 MK at 1.025+-0.025R, to 1.45+-0.2MK at 1.075+-0.025 R consistent with previous observations, and the limb brightening analysis.
Update 12-Oct-96
A paper just before submission to APJL.
YOHKOH SOFT X-RAY DETERMINATION OF PLASMA PARAMETERS IN A POLAR
Carl A. Foley and J. Leonard Culhane
Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Surrey RH5 6NT, UK
Loren W. Acton
Department of Physics, Montana State University, Bozeman, MT 59717, US
The Yohkoh Soft X-ray telescope has been used to study the emission from a polar coronal hole which was clearly visible in October, 1992. Higher temperature mission from diffuse coronal structures in the line of sight can interfere with attempts to measure properties of the coronal hole plasma. Yohkoh coverage of the sun in the period before the observation indicated that the north polar region was free of such contamination. The intensity data were compared with a solar wind model and were found consistent in particular with the predicted variation of intensity with height and with the limb brightening after X-ray scattering of emission from the rest of the disc by the telescope surfaces had been allowed for. Electron temperatures estimated by the filter ratio method were also found consistent with the model and with an in-situ estimate of the maximum temperature in the solar wind by the Ulysses ion charge composition instrument. The presence of material at lower temperatures in the solar wind is not excluded by these observations and the use of differential emission measure analysis with high resolution spectroscopic data from the SOHO mission is proposed to study this problem further.