Abstracts:

   I will describe the rationale and scope of this Meeting

   I will present selected technical details of the RESIK construction and the interface to the CORONAS-F satellite and telemetry system SSNI. I will explain the physical meaning of scientific and auxiliary data being collected.

    RESIK is one of the most advanced and therefore complicated X-ray spectrometers launched. Its construction directly related to the Yohkoh BCS. Understanding various instrumental and physical factors contributing to the measured signal took a lot of time. At present we hope to understand most of the first-order spectra-contaminating effects which have to be taken into account in the process of spectra reduction and calibration. I will discuss some of them in more details including crystal reflectivities, fluorescence, "fixed pattern structure" etc. I will also present some of the instrumental effects which we unveiled recently doing RESIK data analysis and outline a number of still unsolved instrumental calibration problems. I shall discuss the advantage and limitations of the forward spectra treatment approach which may lead to massive RESIK spectra fitting in the future.

   An interactive module of RESIK data visualization and reduction will be presented in real time. Present program options will be shown and discussed. Directions of future improvements will be outlined.

   RESIK is a unique Bragg bent crystal spectrometer covering four soft X-ray selected to cover the spectral ranges from 3.2 A to 6.1 A. From August 2001 to mid-May 2003 RESIK has been collecting solar spectra from active region and flaring plasma. The catalogue which has been built based on RESIK data will be introduced and a number of representative observations covering a wide range of solar activity levels will be presented. Examples of spectra obtained during flares of various importance as well as during exceptionally quiet activity periods will be shown.

    In the spectral range covered by RESIK (3.2 A to 6.1 A) there are many strong emission lines corresponding to H- and He-like resonance transitions of Si, S, Ar and K ions. The identification of these lines will be presented. The lines are supposed to be formed in thermal plasma of temperature between 3 MK and 30 MK and therefore their analysis should reveal the distribution of plasma with the temperature over this broad temperature interval. The presence of lines from various elements allows for the analysis of their abundances. The elements contributing to RESIK measured spectra have a wide range of respective first ionization potentials (FIP) making it possible to study the contribution of FIP effect to the observed abundance variability.

    RESIK collected numerous spectra of active regions and flares in the wavelength range 3.3 A to 6.1 A. This range includes many strong emission lines due to transitions 1s2- 1s(np) and 1s - np, in He-like and H-like ions respectively; the n = 2 and 3 lines are routinely observed for Si, S and Ar ions. For some flares we have observed enhanced emission in spectral features coinciding with these transitions for n up to 9 or 10. We present and discuss identification of these features and comparison of the intensities of observed and theoretical ratios.

    In this talk I will describe the CHIANTI project, with particular emphasys on the latest CHIANTI version and on the improvements done for X-ray line spectroscopy.

   The purpose of this work has been to try to take the advantage of CHIANTI (database, software) to compute the synthetic spectrum for the non-thermal electron distributions. However, the CHIANTI database contains only the collision strengths averaged through Maxwellian distribution. The functional form of the approximation by Abramowitz and Stegun (1965) has been used to evaluate the approximation for Omega from CHIANTI by inverse technique. Computed Omega-s have been compared with known data. The modification of CHIANTI codes which uses derived approximations of Omega allows to compute synthetic spectra for the power and kappa electron distribution very quickly. The main variations in the synthetic spectrum for different distribution function are due to changes in the ionization equilibrium. The influence of the changes in excitation equilibrium is usually lower. The impact of the different non-thermal electron distribution on the synthetic spectrum is showed.

   I report on the temperature distribution of the plasma emission measure (DEM) obtained from the analysis of coronal data. I discuss the DEM of X-ray flares as derived from the analysis of Yohkoh/SXT data and the DEM of quiescent coronal loops obtained from the analysis of SoHO/CDS data.

   In this talk we present calculations of DEM shape obtained for flares observed by RESIK. For computations we use Withbroe-Sylwester multiplicative algorithm. In the set of selected bands used for the DEM analysis the fluxes consist of line and continuum emissions. The appropriate emission functions have been calculated using CHIANTI package.

    We report new results of investigations of the solar corona by the method of XUV imaging spectroscopy with the SPIRIT complex. The experiment is carried out aboard the CORONAS-F satellite launched in July, 2001. The main feature of the experiment is a simultaneous registration of solar images in 11 independent channels which allows studying full solar disk and over-limb structures in narrow spectral bands and monochromatic lines in spectral bands 8.41-8.43 Å, 177-207 Å and 280-335 Å. The investigation has been done during maximum and decay phases of 23rd cycle of solar activity and allow to study as extreme events like flares, coronal mass ejections (CME) associated phenomena and long duration events like development of coronal holes. Spectral diagnostics of some of this structures has been done.

   The SPIRIT is a complex of space telescopic and spectrogeliographic instruments that was created in the Laboratory of X-Ray Astronomy of the Sun (XRAS) of the Lebedev Physical Institute of Russian Academy of Science with a participation of scientific groups from other countries. The SPIRIT was launched on the August 2001 aboard the satellite CORONAS-F and continues to work at the Earth orbit till now. During more than 4 years, SPIRIT obtained about 300 000 images of the Sun in the 10 XUV-channels. All these data are included now in the SPIRIT database, most part of which is free for use and for downloading. We review here the structure and contents of SPIRIT database and describe the main possibilities for data search, access, downloading and processing. The experience of the work with the SPIRIT data will be used by us to create the TESIS Data Center, which is already starting to develop and will be available within several weeks after the TESIS launch.

    More than 300 full-Sun images in monochromatic EUV lines have been obtained by the spectroheliograph RES-C for the current experiment SPIRIT on CORONAS-F mission since the launch on July 31, 2001. About 30 images contain flares at the different phases. The RES-C device includes two channels covering spectral bands 177 – 207 and 285 – 335 Å. Non-overlapping images in the most prominent lines have been recorded in each channel due to about 20 times compression of the solar disc along the dispersion direction. Spatial resolution in the direction perpendicular to the dispersion plane is up to 5 arcsec. About 165 lines are recorded in the both spectral region and 102 lines of He, Ni, Fe, S, Ar, Ca, Cr, Si, and Mg ions with the temperature of formation in the range 0.05 – 20 MK are identified with the help of the CHIANTI database (version 4.2). Relative intensities of 15 prominent lines are used for density diagnostics of optically thin plasma of quiet-Sun areas, active regions and flares. The comparative differential emission measure (DEM) analysis for the flare and active region plasmas have been performed by means of two inversion techniques, the original one based on the Bayes algorithm and that provided by the CHIANTI package.

   In the present paper a short overview is given for the main methods and results of modeling for some plasma structures in the solar corona, observed in the experiment SPIRIT by means of the spectroheliograph RES. This device, being unique in the world practice, made it possible to measure simultaneously about 150 full-Sun monochromatic images in EUV lines in the region 175-205 and 280 – 330 A, as well as in the X-ray line of the Mg XII line at 8.42 A. For the period since the launch of the satellite, 31 July 2001, more than 300 thousands of spectroheliograms have been registered with high temporal resolution by the RES device. These spectroheliograms provided a basis for creation of a unique data bank which made it possible to study the characteristics of both – known plasma structures in the solar corona (active regions, coronal holes) as well as new type of transients, firstly observed in the X-ray monochromatic images: so called “spiders” “hot clouds and other dynamical phenomena with life-time from minutes up to days. EUV spectra have been used for the determination of the distributions for the electron density and the differential emission measure (DEM) with the temperature for various plasma structures, observed in the X-ray channel of RES: active regions, flares and “spiders”. The comparison of the temporal profiles of full-Sun fluxes from X-ray channel of RES with GOES and YOHKOH/SXT data made it possible to determine temperature distribution of different plasma structures versus time and space. The results of modeling of physical conditions in the emitting plasma were used for the analysis of the mechanisms of formation and dynamics of plasma structures, discovered in the X-ray full-Sun monochromatic images.

    The main photometric parameters of the SPIRIT EUV telescopes aboard the CORONAS-F satellite are analyzed and compared with the SOHO/EIT ones. The intercalibration of both instruments has been done using the data of their parallel observations of the Sun in the period from August 2001 till August 2003. In particular, using the ratio of total solar EUV fluxes of corresponding SPIRIT and EIT channels, the SPIRIT data were corrected for non-linearity, long-term recession of conversion factors and its short-term variations with the instrument temperature during the non-obscured orbits of CORONAS-F. After corrections, the relative values of the SPIRIT and EIT EUV fluxes well agree within 8-26%. In the period of December 2002 - February 2003 the EIT data showed some deviations from corresponding SPIRIT values, possibly, due to inaccuracy in calibration of EIT. The variation of the total solar EUV flux in 2001-2005 and its comparison with the GOES X-ray data are presented.

   We use diffraction effects seen in TRACE data for simultaneous imaging and spectroscopic analysis of TRACE observed flare kernels in EUV energy range. Updated model of the TRACE PSF function is used in order to study TRACE diffraction pattern and determining plasma parameters (T/EM) of TRACE observed flare kernels. A review of TRACE flare observations with strong diffraction effects is shown. Future perspectives for applications of the developed data analysis methods are discussed.

   I report on the temperature distribution of the plasma emission measure (DEM) as derived from modeling coronal plasma. I compare the DEM expected from non-confined flaring plasma with that from plasma confined in flaring loops. I discuss the DEM obtained from modeling a stellar flare observed on Proxima Centauri with XMM-Newton. I also discuss the DEM expected from modeling loops heated by nanoflares located at the footpoints as compared to the DEM derived from observations of the coronae of active stars.

   Powerful solar flares (or their episodes) contain impulsive phase and the subsequent development of giant post-eruptive loops. We sustantiate application of the numerical gas-dynamic (non-MHD) simulation for different phases of flares. In particular, Grechnev et al.(2005) showed from the CORONAS-F data that a post-eruptive arcade is developed when the gas-to-magnetic pressure ratio (beta) is close to 1. We used the Jakimiec' model for series of homological flares and obtained a conclusion that gives evidences for relation between impulsive and post-eruptive processes during large flares. We discuss how the RESIK data can be used for estimation of amount of the gas evaporated in the pulse of the flare on August 25, 2001. This allows us to compare this mass with the amount of plasmas that emites during the post-eruptive phase.

   Electron beams propagating during the solar flares cause heating of the solar atmosphere and also modify atomic level populations via collisional processes. Using the approach of NLTE radiative hydrodynamics, we show the influence of the electron beams on the Halpha line profile in numerical simulations of such beam heating. The talk will focus mainly on the effects of the non-thermal collisional rates and the return current on the Halpha spectral line profile. Based on our results, a diagnostic method for determination of the electron beam presence in the formation regions of the Halpha line will be suggested.

   We discuss briefly new results of stellar activity investigations and reveal how typical are active processes on the Sun among phenomena on other late-type stars. Features of powerful solar flares are compared with flares on red dwarf and late-type subgiant stars. We discuss two ways of stellar flare development by examples of the large fast event on EQ~Peg and the long-duration X-ray flare on UX~Ari.During the EQ Peg flare a system of hot coronal loops is formed, but cools down rapidly and decays. Such flares are similar to compact solar flares while long-duration X-ray flares on subgiants as a more energetic analog of flares in complexes of activity on the Sun. These conclusions concerning stellar flares can be fruitful in order to clear up a role of magnetic fields of various scales in flare processes on the Sun.

   We show simultaneous X-ray observations of a flare event on 2003 January 7. In the soft X-rays we use GOES and RESIK data in order to derive temperature and emission measure for the flare plasma. RHESSI fluxes are used for determining temperatures and emission measures in harder X-ray energy bands. The results from all the three instruments are then compared. Differences between X-ray flare characteristics in the impulsive and gradual phase are discussed also.

    The solar flare 4--10 keV (1-3 A) X-ray spectrum is ideal for diagnosing the hottest part of the flare plasma. RHESSI and RESIK observations of the Fe (6.7keV) and Fe/Ni (8keV) features have been analyzed to give Fe abundances in flare plasmas which appear to be near-coronal (4 times photospheric) in most cases. An outline of DEM functions deduced from simultaneous GOES observations and their application to RESIK and RHESSI observations will also be given.

   RHESSI was launched in February 2002 and continues to make imaging and spectroscopic observations of solar flares in both X-rays and gamma rays. Free-free and free-bound continuum together with emission lines are seen in the 'soft' X-ray range (~5 - 20 KeV) from flare plasmas with temperatures from ~ 7 MK to tens of MK. Comparisons between the lower end of RHESSI spectral range and RESIK channels 1 - 4, in 1st order diffraction, provide a useful means of cross-calibration. Also, Fe XXV line emission at ~ 6.7 keV seen by RESIK in 3rd order diffraction, enables cross-calibrations with RHESSI Fe fluxes observed with a 1 keV FWHM resolution above the continuum. Instrumental effects on RHESSI's low energy limit, such as attenuators present during intense flares, will be discussed. An overview of the RHESSI data access and the analysis software will also be given.

    We will discuss how the satellite-to-resonance line ratios may depend on the local properties of the electron distribution functions. The starting point for these considerations are the laboratory EBIT measurements, which we adopt for modeling of the spectral shapes to be measured by RESIK with locally strongly non-Maxwellian electron distributions. The importance of dielectronic satellite line relative intensity analysis will be discussed in a new perspective.

   The Solar-B satellite will be launched in September 2006. This is a joint Japanese/USA/UK collaboration, which follows on from YOHKOH. The Solar-B payload will comprise three instruments: the Solar Optical Telescope, the X-ray Telescope and the EUV Imaging Spectrometer (EIS). SolarB is designed to study the magnetic linkage between the photosphere and the corona. EIS is designed to determine the physical parameters of features in the solar atmosphere (temperature, density and flows). It will cover the wavelength ranges 163-209 A and 242-289 A, which contain many coronal spectral lines.

    A new Russian space mission CORONAS-Photon (2007 launch) is under development. The project is aimed on the space investigations of active processes on the Sun in the maximum of 24th cycle of activity. The new imaging/spectroscopic XUV instrument TESIS (TEleScope / Imaging Spectrometer) is preparing for the mission in P.N. Lebedev Physical Institute. The goal of the experiment is to study the structure and the dynamics of the solar atmosphere over a broad range of heights and temperatures using full Sun XUV spectroscopic imaging. The instrument includes several telescopic and spectrogeliographic channels and covers the spectral range from 8 to 350 A. The instrument will register images of the full Sun and solar corona up to 5 radii in narrow spectral band and monochromatic lines simultaneously in several channels. The detailed description of the instrument is presented.

    A short description will be given of the Polish spectrophotometer SphinX. It is considered to be a part of the Russian TESIS complex and will be used primarily for the flare watch. The instrument will be equipped with two PIN-diode sensors, providing energy esolution of 150-170 keV in the spectral range 0.5 - 10 keV. The spectra will be taken up to 100 times per sec. A special calibration/measurements module will be incorporated for studies of fast spectra variability in a set of narrow (~0.1 keV), well defined spectral bands.