Total mass of six quiescent prominences estimated from their multi-spectral observations

Abstract

Context. Total masses of six solar prominences were estimated using prominence multi-spectral observations (in EUV, X-rays, Hα, and Ca ii H). The observations were made during the observing campaign from April through June 2011. Aims. The aim of the work was to apply a complex method for the prominence mass estimations that can be used later for other prominences observed during the observing campaign. Methods. Our method is based on the fact that intensity of the EUV solar corona at wavelengths below 912A is reduced by the absorption in resonance continua of hydrogen and helium (photoionisation) and at the same time also by a deficit of the coronal emissivity in volume occupied by the cool prominence plasma. Both mechanisms contribute to intensity decrease simultaneously. The observations in X-rays allow us to separate these mechanisms from each other. Coronal emission behind a prominence is not estimated by any temporal or spatial interpolation, but by using a new method based on comparing the ratio of the optical thickness at 193A and 211A determined from the observations with the theoretical ratio. Results. Values of the total mass estimated for six prominences are between 2.9 × 10 11 and 1.7 × 10 12 kg. The column density of hydrogen is of the order of 10 18 −10 19 cm −2 . Our results agree with results of other authors. Conclusions. The method is now ready to be used for all 30 prominences observed during the campaign. Then in the near future it will be possible to obtain a statistics of the total mass of quiescent solar prominences.