We describe the RESIK (REntgenovsky Spektrometr s Izognutymi Kristalami) instrument, consisting of two double-channel X-ray spectrometers, designed to observe solar active region and flare plasmas. RESIK is one of the instruments making up the scientific payload of the Russian CORONAS-F solar mission. The uncollimated spectrometer uses two silicon and two quartz bent crystals observing flare, active region and coronal spectra in four wavelength bands with a resolving power (λ/ λ) of ∼1000. The wavelength coverage, 3.3 -6.1Å, includes emission lines of Si, S, Cl, Ar, and K and in the third diffraction order, the wavelength range includes He-like Fe lines (1.85Å) and Ni lines (1.55Å) with dielectronic satellites, emitted during intense, hot flares. The instrument is believed to be the best calibrated space-borne crystal spectrometer flown to date. The spectrometer dynamically adjusts the data gathering intervals from 1 s to 5 minutes, depending on the level of solar X-ray emission at the time of observation. The principal aims of RESIK are the measurements of relative and absolute element abundances in the emitting plasma and the temperature distribution of plasma (differential emission measure) over the temperature interval 3 and 50 MK. This paper summarizes the scientific objectives of RESIK and describes the design, characteristics, and performance of the instrument.

The first 2‐D distributions of the polarization angle and of the relative color index for the K‐corona of 29 March 2006 are presented. The distributions illustrate the efficiency of the total solar eclipse approach for high‐precision measurements of the K‐corona continuum in the range < 1.4 R⊙. Natural ground and space total solar eclipses caused by external occulting the bright solar‐disk light by the Moon or Earth group planets are discussed. Calculations of the eclipse magnitude m are carried out to show ideal conditions for total solar eclipse observations in space from Lagrange point L2 for Mars (m ≈ 1.025). The illumination in Mars' shadow is estimated to equal 5.6 × 10−11 for the wavelength of 550 nm. No internal or external occulting coronagraphs are needed. Partial solar eclipses with m > 0.91 can be observed from Lagrange points L2 for Mercury, Venus, and Earth.

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Large photoinduced transmission and reflection is observed in porous silicon (PS) films in the spectral region 1.6–3.2 eV by using a femtosecond pump-supercontinuum. probe technique. The measured nonlinear transmission and reflectivity spectra have a fast component ~500 fs. The spectral structure and relaxation dynamics of the short-lived component with slowing down of relaxation rate at ~1.95 eV and ~2.5 eV are suggestive that relaxation processes correspond to nanocrystallites defects scattering. Observed coherent phonons vibrations at 518 cm-1 and 480 cm-1 may be attributed to the size of crystallites ~5 nm and due to presence of a disordered phase, respectively.

Abstract.A multi-channel SPIRIT telescope/spectroheliograph aboard the CORONAS-F satellite operating in soft X-ray and EUV ranges is an effective instrument for complex studies of CME-associated phenomena such as eruptive filaments, dimmings, coronal waves, posteruptive arcades, etc. In particular, SRIRIT observations of high-temperature (T = 5-15 MK) plasma structures in the MgXII 8.42Å line show specific pre-CME sigmoid magnetic field configurations. Eruptions of filaments (prominences) and dimmings in a CME process are seen with a high contrast in the coronal 175Å band (FeIX-XI) and the transition-region 304Å (HeII) images. Our results are illustrated by several powerful eruptive events of the current solar cycle. We compare SPIRIT data with observations at other spaceborne and ground-based instruments (SOHO/EIT, Yohkoh/SXT, and Hα images, etc.)