Investigations of Physical Processes in Solar Flare Plasma on the Basis of RESIK Spectrometer Observations

Simultaneous registration of spectra of quickly varying sources may be obtained through the use of curved fixed crystals instead of the scanning flat crystals spectrometer. Illuminating such a curved crystal with parallel X-ray beam allows to obtain, after the reflection, the whole spectrum covering certain wavelengths range, as the incidence angle at curved crystal surface represents a monotonous function of incidence point position measured along the crystal. The RESIK bent crystal spectrometer was developed in Poland with the help from experts of Naval Research Laboratory (USA), Rutherford Appleton Laboratory (UK), and Mullard Space Science Laboratory (MSSL, UK). The development work was also supported by scientists of Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Waves Propagation of the Russian Academy of Sciences. Unique RESIK spectra and the results obtained are presented and discussed.