A crystal spectrometer has been flown on a sounding rocket to study the soft X-ray line emission from the sun. Collimators, with a field of view 9 arc min square, allowed individual active regions to be observed. A detailed description of the instrument is given. Solar conditions at the time of launch are then discussed, together with a brief history of the three active regions studied. It is shown that the collimators performed satisfactorily. The spectrum of an active region is used to identify the important solar line emission, and a comparison of the spectra obtained near 1.7 nm is made. The temperatures of the regions are discussed, and it is shown that a non-isothermal model is required. A good correlation is found between the soft X-ray emission and other solar observations.
A rocket-borne, collimated spectremeter 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 ~ 101~ cm-3 and temperatures of at least 4 • 10 6 K. Even the third region, which was much less impressive and quite compact in Ha, appears to have had a small amount of this dense plasma in its central core.
Work has been in progress for many years at University College London to determine how the intensity spectrum of emitted X-rays changes as a function of time and position on the solar disk. Early spectroheliographs consisted of grazing incidence parabolic mirrors which focussed radiation onto proportional counters from which spectral data were obtained. Such instruments, built in collaboration with the University of Leicester Group, have been flown on two rockets (Negus et al., 1969) and on the OSO V satellite (Herring et al., 1971).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.