Comparative Study of the Three-Dimensional Thermodynamical Structure of the Inner Corona of Solar Minimum Carrington Rotations 1915 and 2081

Using differential emission measure tomography (DEMT) based on time series of EUV images, we carry out a quantitative comparative analysis of the three-dimensional (3D) structure of the electron density and temperature of the inner corona (\(r<1.25\,\mathrm{R}_{\odot}\)) between two specific rotations selected from the last two solar minima, namely Carrington Rotations (CR)1915 and CR-2081. The analysis places error bars on the results because of the systematic uncertainty of the sources. While the results for CR-2081 are characterized by a remarkable north–south symmetry, the southern hemisphere for CR-1915 exhibits higher densities and temperatures than the northern hemisphere. The core region of the streamer belt in both rotations is found to be populated by structures whose temperature decreases with height (called “down loops” in our previous articles). They are characterized by plasma \(\beta\gtrsim1\), and may be the result of the efficient dissipation of Alfvén waves at low coronal heights. The comparative analysis reveals that the low latitudes of the equatorial streamer belt of CR-1915 exhibit higher densities than for CR-2081. This cannot be explained by the systematic uncertainties. In addition, the southern hemisphere of the streamer belt of CR-1915 is characterized by higher temperatures and density scale heights than for CR-2081. On the other hand, the coronal hole region of CR-1915 shows lower temperatures than for CR-2081. The reported differences are in the range \({\approx}\,10\,\mbox{--}\,25\%\), depending on the specific physical quantity and region that is compared, as fully detailed in the analysis. For other regions and/or physical quantities, the uncertainties do not allow assessing the thermodynamical differences between the two rotations. Future investigation will involve a DEMT analysis of other Carrington rotations selected from both epochs, and also a comparison of their tomographic reconstructions with magnetohydrodynamical simulations of the inner corona.     

Estimates of the radii,masses, and luminosities of LAMOST stars

Based on the spectral observations of the LAMOST (DR2) survey, the radii, masses, and luminosities of 700 481 stars were estimated. These stars belong to spectral types A, F, G, and K, and have metallicities between ?0.845 and 0.0. To determine the properties of the stars, we used up-to-date models of the stellar interior structure, computed with account for the stellar evolution rate and the initial mass function. The use of evolutionary estimates for two types of stars—with and without rotation—allowed us to account for the uncertainty associated with the lack of data on the rotation velocity of the stars under consideration. The obtained stellar radii, together with the photometric estimates of interstellar extinction and angular diameters can be used to study the dependence of interstellar extinction on distance as well as to estimate the stellar distances.     

Stars with discrepant <Emphasis Type="Italic">v</Emphasis> sin <Emphasis Type="Italic">i</Emphasis> as derived from the Ca II 3933 and Mg II 4481 Å lines. VI. HD 199892 — an SB2 spectroscopic binary

We analyzed the spectra of a well known SB1 binary HD199892 for which the projected rotational velocity v sin i, introduced in the literature, significantly differs when determined from the lines of Ca II at 3933 Å and ofMg II at 4481 Å. Contrary to the former findings, we discovered the signs of spectral lines of a companion star in the profile of Hβ as well as weak metallic lines in the high resolution high S/N spectra covering the most of the visual region. We estimated the secondary star to be a main sequence A4V star with a mass of 2.2M _⊙ and derived its radial velocity which resulted in the mass of the primary M = 4.6M _⊙. Short sections of the spectra in the Mg II 4481 Å and Ca II 3933 Å regions are analyzed as well.     

SPEXTRA: Optimal extraction code for long-slit spectra in crowded fields

We present a code for the optimal extraction of long-slit 2D spectra in crowded stellar fields. Its main advantage and difference from the existing spectrum extraction codes is the presence of a graphical user interface (GUI) and a convenient visualization system of data and extraction parameters. On the whole, the package is designed to study stars in crowded fields of nearby galaxies and star clusters in galaxies. Apart from the spectrum extraction for several stars which are closely located or superimposed, it allows the spectra of objects to be extracted with subtraction of superimposed nebulae of different shapes and different degrees of ionization. The package can also be used to study single stars in the case of a strong background. In the current version, the optimal extraction of 2D spectra with an aperture and the Gaussian function as PSF (point spread function) is proposed. In the future, the package will be supplemented with the possibility to build a PSF based on a Moffat function. We present the details of GUI, illustrate main features of the package, and show results of extraction of the several interesting spectra of objects from different telescopes.     

Technologies of measurements of the sea level

We analyze the contemporary methods and means of measurements of the sea level and inland waters, describe a CTD-meter designed at the Marine Hydrophysical Institute of the Ukrainian National of Science for the determination of the sea level, formulate the requirements to the perfect meter of the water level, and demonstrate that an electronic sounding stick based on the distributed Walsh thermoprofilometers can play the role of a device of this kind.     

New results on large-scale structures

A new version of the magnetic-tape catalog of ABELL clusters of galaxies is used to obtain redshift estimators and to generate two samples of clusters. A procedure for searching for superclusters of galaxies is applied and the results are given in tabular and graphic form. For a lmited homogeneous sample (distance 60–275 Mpc, galactic latitude B > 35°), 12 multiplets, having member clusters with known redshifts, are found. It is shown that the spatial covariance function for rich clusters has the form ξ = (r₀/r)γ with r₀ = 22.4 ± 1.8 Mpc and γ = 1.90 ± 0.25 for 3 Mpc ≲ r ≲ 80 Mpc.     

Regional variations in cleavage and fold development in North Wales

The arcuate pattern of the main Caledonian cleavage and associated fold axial plane traces in North Wales is due partly to NW-SE compression with tectonic transport to the southeast against the concealed crop of the Tan y grisiau Microgranite. Low-angle cleavage close to the microgranite is shown to be a local variant of the regional cleavage formed during the main deformation and not an earlier phase as previously supposed. Transcurrent movements along several major fault systems are also related to compression around the microgranite and the Harlech Dome block.