Crystal spectrometer studies of the Sun employing a rotation modulation collimator

The use of rotating modulation collimators in high resolution solar X-ray spectroscopy is discussed with reference to the recent flight of a sounding rocket payload. This rocket carried an experiment which combined a modulation collimator and a Bragg crystal spectrometer to make moderately high resolution spectral and spatial measurements simultaneously. The response of the instrument to extended sources is described. It is shown that the technique is particularly suited to long term observations of active region emission, but that useful measurements can be made even during a short rocket flight.Our observations were made in 1972 October 26 between 0432 UT and 0436 UT. During the flight a scan of the solar X-ray spectrum was made which covered the wavelength range 1.45–1.71 nm. A small flare commenced at about 0432 UT in McMath calcium plage region 12094; the emission from this provided the major contribution to the observed spectrum. X-ray emission from a group of active regions in the SW and the small McMath region 12090 has also been detected.Spectral and spatial observations have been combined to investigate the conditions in both active region and flare plasmas.     

A comparison of three solar active regions based on their soft X-ray line spectra

A rocket-borne, collimated spectrometer has obtained the soft X-ray (1.0–2.2 nm) spectra of three solar active regions. The principal features of the spectra are described and are then used to determine the conditions in the active regions. An isothermal (single temperature) model is not able to describe the observed spectra so that a continuous distribution of emission measure with temperature is introduced.This distribution, based on that proposed by Chambe, is then used to investigate the structure of the active regions. Several simple models are considered. It is shown that each active region has a hot, dense core surrounded by a large outer volume through which the temperature and density fall until normal coronal conditions are reached.Two of the regions exhibited similar characteristics with the cores having electron densities 10¹⁰ cm^–3 and temperatures of at least 4 × 10⁶K. Even the third region, which was much less impressive and quite compact in H, appears to have had a small amount of this dense plasma in its central core.