Showing papers by "J. Lang published in 2001"
Journal Article•
16 citations
TL;DR: In this paper, a model ion, constructed using the best available atomic data, is used to predict the line intensity ratios for a wide range of electron temperatures and densities. And the usefulness of the ratios for electron temperature and density diagnostics, as well as for spectrometer calibration, is discussed.
Abstract: New measurements of line intensity ratios in the Be-like ion Si xi are presented for observations of the quiet Sun, active regions, coronal holes and above-limb regions obtained using the Coronal Diagnostic Spectrometer on the Solar and Heliospheric Observatory. A model ion, constructed using the best available atomic data, is used to predict the line intensity ratios for a wide range of electron temperatures and densities. Comparisons of the theoretical ratios with the new intensity ratios as well as with those from previous solar observations and laboratory measurements are given. The usefulness of the ratios for electron temperature and density diagnostics, as well as for spectrometer calibration, is discussed.
5 citations
TL;DR: In this paper, CDS and SUMER data from the SOHO mission were used to study the long-term variability of the Sun's long term variability and its temporal correlation.
Abstract: Since the beginning of the SOHO (Solar and Heliospheric Observatory) mission an intercalibration programme was carried out which included simultaneous observations of the EUV instruments CDS (Coronal Diagnostic Spectrometer) and SUMER (Solar Ultraviolet Measurements of Emitted Radiation) of common targets on the quiet Sun The observations in the chromospheric line of He i (584 A) and the two coronal lines of Mg x (609 A and 624 A) thus cover the long period of 4 years and provide a data set highly suitable not only for instrumental comparison but also for studies of the quiet Sun’s long term variability Up to the SOHO accident, both instruments show a very good temporal correlation and stability Even after the loss and recovery of the spacecraft, when the instruments had been exposed to extreme temperature conditions, the performance of the CDS and SUMER instruments is still good, as is the temporal correlation However, the ratio between the efficiencies of the two instruments, which remained constant with time until the SOHO accident seems to have changed afterwards In the coronal lines both instruments show an increase of average radiances towards the solar maximum