Showing papers in "Kinematics and Physics of Celestial Bodies in 2014"

Ionosphere disturbances accompanying the flight of the Chelyabinsk body

Abstract: Data received from a network of ionosondes located at distances of 1500–3100 km from the Chelyabinsk meteorite site are used to analyze ionospheric disturbances at a height of approximately 300 km following the flight and explosion of the space body. The fall of the meteoroid is believed to be accompanied by the generation of gravitational waves in the neutral atmosphere and traveling ionospheric disturbances. The velocity and period of the latter are 600–700 m/s and 70–135 min, respectively; the amplitude of relative electron concentration disturbances is 10–20%. There is evidence of the 6–7 h ionospheric presence of wave electron concentration disturbances with relative amplitude of 10–20%, which could have been caused by long-living whirlwinds in the upper atmosphere.

On the structure of azimuthally small-scale ULF oscillations of hot space plasma in a curved magnetic field. Modes with continuous spectrum

Abstract: The problem of propagation of azimuthally small-scale ULF modes in plasma with 1D inhomogeneity and variable curvature of magnetic lines of force is analyzed. The propagation regions and the transverse structure of stable Alfven and cusp modes, as well as unstable ballooning modes, are determined. It is shown that long-living ballooning and cusp modes can exist. Our results qualitatively describe the behavior of ULF modes with continuous spectrum in the geomagnetosphere and can be used for interpretation of spacecraft and SuperDARN radar measurement data.

Dynamic and spectral X-ray features of the microquasar XTE J1550-564

Abstract: Memory function formalism is used to investigate the dynamic and spectral features (including a quantitative comparison of the decay of correlations and statistical memory) of the time discrete X-ray signals from the microquasar XTE J1550-564. The X-ray dynamics has been recorded aboard the Rossi X-Ray Timing Explorer. Temporal and event correlations are analyzed to find distinct patterns in the relaxation processes and memory effects in the equi- and nonequidistant dynamics of the X-ray flux from XTE J1550-564. The described method can be used to study a wide range of astrophysical phenomena and processes associated with event representation.

Compiling catalogs of stellar coordinates and proper motions via coprocessing of archival photographic and modern CCD observations

Abstract: A catalog of positions and proper motions of stars in the fields around open clusters was compiled at the Research Institute—Nikolaev Astronomical Observatory (NAO) with the use of the results of photographic observations conducted in the 20th century (at the NAO zonal astrograph with D = 11.6 cm and F = 2.04 m) and modern CCD observations performed with the Mobitel NAO telescope (D = 50 cm and F = 3 m) with a Alta U9000 3056 × 3056 CCD camera. The difference in epochs is approximately 30 years. The initial processing of photographic images was carried out with the use of the MIDAS/ROMAFOT software package, and the CCD data were processed using the Astrometrica software. The data reduction and integration was performed with the use of proprietary software. A photographic catalog of approximately 900000 stars (8–16m, J1981.6) and a CCD catalog of 780000 stars (9–17m, J2012.2) were obtained, and the integrated catalog of positions, proper motions, and stellar magnitudes of approximately 700000 stars up to 17m was then compiled. The errors in catalog positions along both coordinates varied from 20 mas (for 8–13m stars) to 40 mas (for 14–17m stars). The standard deviation of proper motions was approximately 5 mas/year along both coordinates. The stellar magnitudes were estimated. The estimated standard deviation of stellar magnitudes in the Tycho-2 system was 0.04m. The catalogs may be accessed from the NAO site.

Determining the effective temperatures of G- and K-type giants and supergiants based on observed photometric indices

Abstract: A method for determining the effective temperature T eff of G- and K-type giants and supergiants is proposed. The method is based on the use of two photometric indices free from the interstellar absorption influence: the Q index in the UBV photometric system and the [c 1] index in the uvby system. Empirical relations between the T eff values found for nearby and bright G- and K-type giants and supergiants with the use of the infrared fluxes method (IRFM), on the one hand, and the observed Q and [c 1] indices for these stars, on the other hand, are plotted. A systematic discrepancy between the dependences of T eff on Q for the stars with standard and reduced metallicities is found. Approximating the plotted dependences with second-order polynomials, one can obtain a relatively simple and a rather accurate method for determining the T eff value in the range of 3800 ≤ T ≤ 5100 K (based on the Q index) or 4900 ≤ T eff ≤ 5500 K (based on the [c 1] index).

Plasma motions in the solar loop of emerging magnetic flux

Abstract: The results of analyzing variations in the line-of-sight (LOS) velocities in the solar loop at photospheric and chromospheric levels in the region of emerging magnetic flux for the evolving active region NOAA 11024 are reported. The analysis combines the data of multiwave spectropolarimetric observations that were carried out on July 4, 2009, (Tenerife, Spain) using THEMIS solar telescope and the data obtained with GOES, SOHO, and STEREO cosmic satellites. A complex sequence of active events has been studied: formation of the Ellerman bomb, B1 X-ray microflare, and four chromospheric surges that were formed as a result of magnetic reconnection caused by new emerging magnetic flux. The Ellerman bomb was formed in the vicinity of a growing pore. Variations in the velocity V LOS of the EB had an oscillation character for chromosphere and photosphere. Before the microflare, the average velocities of the upward and downward plasma fluxes in one leg of the magnetic loop were nearly the same—26 km/s. During the microflare, the velocity V LOS of the ascending and descending flows increased up to −33 and 50 km/s, respectively. Variations in line-of-sight velocity of a plasma in the second leg of the magnetic loop correlated well with variations of V LOS in the region of microflare, but they occurred 1.5 minutes later. During the time of observations, four chromospheric ejections of matter were formed and three of them occurred in the region of Ellerman’s bomb formation. Sharp variations in the soft X-ray intensity occurred during these ejections. At photospheric level, variations in the line-of-sight velocity of plasma in the legs of the loop occurred in the opposite direction. In the region of the first leg, velocity V LOS diminished from −1.8 to −0.4 km/s, while the velocity increased from −0.6 to −2.6 km/s in the region of the second leg.

Polarimetry of the E-type asteroid 64 Angelina

Abstract: Results of polarimetric observations of a high-albedo asteroid 64 Angelina obtained in the phase-angle range from 0.8° to 24.3° are presented. The observations were carried out in the period from September 28 to October 9, 2008, and on November 15, 2011, and September 18, 2012, with the 1.25-m and 2.6-m telescopes of the Crimean Astrophysical Observatory equipped with a five-color double-beam photopolarimeter and a single-channel photometer-polarimeter, respectively. Our observations confirm the polarimetric opposition effect in asteroid 64 Angelina at small phase angles and well agree with the other observations. The obtained results are discussed in terms of the currently available models of the light scattering by regolith surfaces.

Specifics of the solar photospheric convection at granulation, mesogranulation, and supergranulation scales

Abstract: The power spectra of temperature and vertical velocity variations in the solar photosphere are calculated using the data obtained through observations of a nonperturbed region near the solar disk center in the neutral iron line λ ≈ 639.3 nm conducted at the 70 cm German Vacuum Tower Telescope (VTT) located in the Canary Islands (Spain). The variations of these spectra with altitude are analyzed. It is found that the primary power in the lower photosphere is localized in the range of frequencies that correspond to granulation with a peak at the λ ≈ 1.5–2.0 Mm scale and is reduced with altitude, the power spectrum maximum in the upper photospheric layers is shifted towards larger scales (Δλ ≤ 1 Mm), and the power of variations of the vertical supergranulation velocity (λ ≈ 20–30 Mm) virtually does not change with altitude. An isolated mesogranulation regime (λ ≈ 5–12 Mm) is not found at any of the studied altitudes. The obtained results suggest that the convective structure of the solar photosphere at mesogranulation scales behaves like granulation: the mesostructures are a part of an extended distribution of granulation scales. It is shown that the supergranulation flows are stable throughout the entire photosphere and reach much higher altitudes than the granulation flows.

Additional Criteria for Identifying the Asteroid Families and Confirmation of the Effect of Spatial Separation of Family Members according to Their Albedos

Abstract: The D(a) distribution of asteroid sizes by their semimajor axes and the N(p) distribution of the number of asteroids by their albedo values for individual families are used to isolate the asteroid families more clearly. The families identified by Masiero et al. (2013) are analyzed with the use of these distributions, and correctly and incorrectly isolated families are found. A reduction in the mean albedo with increasing semimajor axis is observed for almost all correctly identified families that are not truncated by resonances. This reduction is statistically significant for the majority of these families. Not a single family exhibits a statistically significant increase in albedo. This confirms our previous conclusions that a nongravitational effect acting in the asteroid belt results in the spatial separation of asteroids with different albedos.

Properties of dispersive Alfvén waves: 2. Kinetics (finite and high density plasmas)

Abstract: The work is devoted to the study of the behavior of dispersive Alfven waves in astrophysical plasma of finite and high pressure. All the main wave characteristics were obtained, namely, the dispersion, fading, polarization, density perturbations, and charge density perturbations. The effect of the parameters of the space environment on the behavior and properties of dispersive Alfven waves was analyzed. The wave behavior in finite and high-pressure plasmas is shown to differ appreciably from the behavior in very low, intermediate, and low-pressure plasmas.

Quantitative analysis of the atmospheric density models applicable for determination of artificial satellite deceleration

Abstract: For determination of Earth orientation parameters with a satellite laser, ranging their motion should be modeled with the precision of the ranging (3–5 mm). For low Earth orbits (1000 km or lower), the procedure needs atmospheric deceleration force. Precise values of the atmosphere density are the main difficulty there. There are a lot of atmosphere density models for heights to 1500 km. This article deals with NRL-MSISE-00, DTM-2012, and JB2008 empirical atmosphere density models, which are applicable for this task. The quantitative analysis of the models’ precision is given, and some recommendations for their use are formulated.

One type of three-wave interaction of low-frequency waves in magnetoactive plasma of the solar atmosphere

Abstract: We study the process of occurrence of “quasi-mode” decay instability of kinetic Alfven waves (KAW) in the chromosphere of a solar active region before a flare, namely, in plasma of magnetic loops near their footpoints. The decay of a primary KAW into a kinetic ion-acoustic wave and a secondary KAW was considered as a specific type of three-wave interaction. Necessary conditions for the KAW decay instability occurrence were found for two semiempirical models of the solar atmosphere with the use of a modified expression for the growth rate of instability in the case of nonlinear interaction of low-frequency waves with an abnormally low excitation threshold. It was shown that the main criteria for the development of this instability significantly depend on the amplitude of external magnetic field in the region under study as well as on a model of the solar atmosphere.

Multicomponent simulation of emission of low-metallicity H II regions

Abstract: Using multicomponent photoionization simulation, we investigated the impact of bubble-like structures around starbursts inside the low-metallicity H II regions on the ionization spectrum shape and emission line forming. Radial distribution of density values and other physical parameters of bubble-like structures were taken from Weaver et al. (Weaver et al., 1977, p. 377). The first and second inner components of such models describe the free expansion zone of superwind from the central starburst region and rarefied hot gas of the cavern thermalized by inverse shock wave, respectively. The gas density and electron temperature distributions into these components are obtained from the solution of the system of equations of continuity and energy transfer, including heat conductivity. The third component is a thin shell of high density gas formed from the gas surrounding a bubble and made by direct shock wind wave. The gas density in this component was obtained from isobaric condition at contact discontinuity between the second and third components. Input spectra of the ionizing radiation were obtained from the starburst evolutional models. The evolution grid of the multicomponent low-metallicity photoionization models with free parameters determining physical conditions inside the bubble-like structure was calculated. The impact of bubble-like structure on the change of ionization spectrum shape and the formation of fluxes of important emission lines in low-metallicity case was analyzed in detail.

Spectrum of comet C/2009 P1 (Garradd) in the optical wavelength range

Abstract: Moderate-resolution spectra of comet C/2009 P1 (Garradd) in the wavelength range from 380 to 540 nm have been analyzed. The spectra were acquired, when the comet was at the distances 1.96 and 1.36 AU from the Sun and the Earth, respectively. The observations were fulfilled in the prime focus of the 6-m BTA telescope (Special Astrophysical Observatory, Russian Academy of Sciences) with the use of the SCORPIO focal reducer. Molecular emissions of C2, C3, CN, CN2, CH, CH+, and CO+ in the cometary coma were identified. In total, 148 emission features were detected. The gas production rate of molecules was determined with the Haser model. The ratios of the gas production rates are log[Q(C2/Q(CN)] = 0.26 and log[Q(C3/Q(CN)] = −1.09. The gas production rates of C2 and C3 molecules are 4.84 × 1026 and 2.16 × 1025 mol/s, respectively.

On the possibility of the development of longitudinal wave instabilities on the background of the small-scale Bernstein turbulence in preflare chromosphere of a solar active region

Abstract: The process of origination and development of instabilities of the longitudinal waves of two types, namely, low-frequency ion-acoustic and high-frequency (“electronic”) Langmuir waves, in the preflare atmosphere of an active solar region are studied. The area under study is located at the chromospheric part of the flare loop near its footpoint. A weak large-scale electric field of flaring loop is the main source of these instabilities. The velocity of an electronic flow in the preflare plasma is supposed to be much lower than thermal electron velocity. Instability development is considered against the background of small-scale Bernstein wave turbulence, which exists in the preflare plasma and has an extremely low threshold of excitation. The necessary conditions for the instability origination and development, as well as the boundary values of the main plasma and wave perturbation parameters, are calculated.

Analysis of the Spectral Energy Distribution of the Peculiar Carbon Giant TU Gem

Abstract: The TU Gem star has long been known as a peculiar carbon giant of the Galaxy halo, but its classification as a CH star is still debated. We estimated the TU Gem atmosphere parameters through modeling its spectrum and comparision one with the spectra of the star observed in two wide spectral ranges (λλ 400–720 nm and λλ 900–2440 nm). The low-dispersion optical TU Gem spectrum obtained by Barnbaum et al. (2006) (R ∼ 600) and the infrared spectrum presented by Tanaka et al. (2007) (R ∼ 2600) were used in the analysis. The model atmospheres were calculated using the SAM12 software (Pavlenko, 2003). Since the metallicity ([Fe/H]) value could not be determined conclusively based on our spectral data, only the TU Gem effective temperature T eff (that depends weakly on metallicity) was defined with certainty (T eff = 3000 ± 100 K). We determined the C/O, [C/Fe], and [N/Fe] values for the −2.0 ≤ [Fe/H] ≤ 0.0 range with a step of Δ[Fe/H] = 0.5. Our estimate of [C/Fe] (0.63–0.67 at [Fe/H] = −1.0) is higher than the corresponding estimate ([C/Fe] = 0.21 at [Fe/H] = −1.1) given in (Kipper et al., 1996), while the estimates for [N/Fe] at the stated metallicities agree with each other: [N/Fe] = +1.0. This brings TU Gem closer to CH stars, but a detailed analysis of the chemical composition of the TU Gem atmosphere is required to reach a definite conclusion.

Charged particle acceleration in the front of the shock wave bounding supersonic solar wind

Abstract: The process of cosmic ray acceleration in the front of the spherical shock wave bounding the supersonic solar wind is studied. On the basis of our analytical solution of the transport equation, the energy and spatial distributions of cosmic ray intensity and anisotropy are investigated. It is shown that the shape of accelerated particle spectrum is determined by the medium compressibility at the shock front and by cosmic ray modulation parameters.

Properties of dispersive Alfvén waves: 3. Hydrodynamics (Very Low, Intermediate, and Low Density Plasmas)

Abstract: The behavior of dispersive Alfven waves (DAWs), including inertial and kinetic Alfven waves, in astrophysical plasmas of very low, intermediate, and low pressure is investigated in the hydrodynamic approximation. New full solutions are obtained. Our results are analyzed and compared with those from the kinetic approach. It is shown that one general solution for the DAWs in plasmas of very low, intermediate, and low pressure can be obtained in the framework of the hydrodynamic approach, as opposed to the kinetic one. In the very low damping region, the kinetic and hydrodynamic solutions agree very well; but there are parameter regions where the solutions are essentially different. The influence of the astrophysical medium parameters on the DAW behavior and properties is analyzed. All main wave characteristics—the dispersion, damping, polarization, density perturbations, and charge density perturbations—are obtained, whose the consideration is very important for the observation and detection of these waves, as well as for a more correct understanding of their behavior and role in various astrophysical processes taking place in the cosmic medium.

Properties of dispersive Alfven waves: 4. Hydrodynamics (finite and high-pressure plasmas)

Abstract: The behavior of dispersive Alfven waves (DAWs) in astrophysical plasmas of finite and high pressure, which have not been considered thus far, is studied in the hydrodynamic approximation. The results are analyzed and compared with those obtained in the kinetic approach. It is shown that one general solution for DAWs in plasmas of finite and high pressure can be obtained using the hydrodynamic approach in contrast to the kinetic one. Kinetic and hydrodynamic solutions correspond to each other very well in a domain with weakly damped DAWs; however, solutions may differ appreciably in some parameter domains, especially in high-pressure plasma. The effect of parameters of the astrophysical medium on the DAW behavior and properties is analyzed. All the main wave characteristics were determined: dispersion, damping, polarization, density perturbations, and charge density perturbations. Since finite-pressure plasma is one of the most frequently encountered states of astrophysical plasma, it is very important to take into account specific features in behavior of these waves for their detecting and a more correct understanding of their behavior and the role they play in different astrophysical processes that occur in space environment.

On the efficiency of polarization measurements while studying aerosols in the terrestrial atmosphere

Abstract: It has been shown that the orbital polarization measurements of the Earth in the spectral range λ > 300 nm do not allow the sets of the Stokes parameters satisfying the homogeneity requirement for the optical properties of the “atmosphere + surface” system to be retrieved. Due to this, the atmospheric and surface contributions cannot be correctly separated and the physical properties of the atmospheric aerosol cannot be determined. This is caused by the optical heterogeneity of the system, the different nature of aerosol above different relief features, and the poorly predictable temporal changes of the optical properties of the “atmosphere + surface” system. Observations at λ < 300 nm are more acceptable, since not only the surface but also the tropospheric layer of the atmosphere, which are both mostly subjected to the effects of horizontal inhomogeneity and temporal variations, become practically invisible due to a high absorption by the ozone layer. Because of this, from the scans along specified latitude zones, one may obtain the quasi-homogeneous dependences of the second Stokes parameter Q(α) (U(α) = 0) suitable for estimating the physical characteristics of the stratospheric aerosol and revealing their horizontal and temporal variations.

Investigation of the Hα spectral line and the Na D sodium doublet in the spectrum of the post-AGB star HD 161796

Abstract: Variability of the profile of the Hα line and the Na D sodium doublet in the spectrum of HD 161796 was studied based on the spectrograms obtained with the 2-meter telescope of Shamakhy Astrophysical Observatory (National Academy of Sciences of Azerbaijan). It was found that the radial velocity and the equivalent width of the Hα line profile and the equivalent width of the sodium doublet vary in synchrony with changes in the V light curve amplitude that occur with a known period P of 62 days. The radial velocity of the D2 line of the sodium doublet (Na I λ 588.9953 nm) varies in antiphase with the variations of the V light curve, the radial velocity of the Hα line, and the equivalent widths of Hα and D2.

On the precision estimation of fundamental planetary ephemerides

Abstract: Precision analysis of the random errors of the heliocentric planetary and geocentric Lunar positions calculated with the DELE423, Inpop 10e, EPM2011, VSOP2013 ephemerides is presented.

Spatial variations of Stokes profiles of magnetoactive lines Fe I

Abstract: Solutions of the polarized radiative transfer problem were obtained within the 3D MHD model of the quiet solar atmosphere. Spatial variations of the Stokes profile parameters caused by the granulation structure and small-scale magnetic fields in the quiet solar photosphere for neutral iron magnetoactive lines are studied. The modulation effect of Stokes V profile parameters (amplitude and area) by the granulation structure of the solar photosphere is revealed. This effect is significant mainly in intergranules, in which the modulation depth reaches 50%. The correlation of Stokes profile parameters with small-scale solar granulation magnetic fields is investigated. It is shown that it is possible to construct calibration relationships that provide the correlation coefficient of 0.98 in diagnostics of small-scale magnetic fields using Stokes profile parameters of Fe I lines λ 525.02 and λ 524.71 nm.

Method for calculating low-velocity bipolar outflow parameters in massive star formation regions

Abstract: New method for calculating parameters of low-velocity components of bipolar outflows in molecular clouds is presented. The method takes into account all possible bipolar flow effects on spectral lines: the line profile asymmetry, the presence of line wings, and the systematic shift of the line profile as a whole along the axis of the outflow. The method is adapted to calculating parameters of weak bipolar outflows and flows with low S/N ratios in their spectra. Using this method, the parameters of bipolar outflows in the source G122.0-7.1 are calculated.

Two-component photosphere models of a 2N/M2-class solar flare

Abstract: Physical state of the photosphere during a 2N/M2 solar flare on July 18, 2000, was studied. We used Echelle Zeeman spectrograms obtained by V. G. Lozitsky in orthogonal circular polarizations with a solar spectrograph. Semiempirical photospheric models were constructed for three moments in time in the initial and main phases of the flare using the SIR code applied to Stokes I and V profiles of seven iron and chromium lines. The photospheric model of the flare contains two components: a magnetic-field component and nonmagnetic environment. The height distributions of the temperature, magnetic field, and line-of-sight velocity were derived. The temperature in the nonmagnetic component had a nonmonotonous run with height. The models include layers in the middle and upper photosphere in which temperature is enhanced relative to an unperturbed photosphere model. As the flare developed, the temperature in the lower layers was increasing by 500–800 K. The magnetic field increased by 0.05 T and 0.08–0.1 T in the lower and upper photosphere during the flare, respectively, with the vertical temperature gradient decreasing from 0.0012 to 0.0008 T/km. The model for the onset phase of the flare indicates that there were upflows and downflows of substance in the lower and upper photosphere, respectively. The flow velocities decreased appreciably in the main phase of the flare. The model parameters of the nonmagnetic environment were only slightly different from those of the unperturbed photosphere.

Gravitational stability of dark energy in galaxies and clusters of galaxies

Abstract: We analyze the behavior of the scalar field as dark energy of the Universe in a static world of galaxies and clusters of galaxies. We find the analytical solutions of evolution equations of the density and velocity perturbations of dark matter and dark energy, which interact only gravitationally, along with the perturbations of metric in a static world with background Minkowski metric. It was shown that quintessential and phantom dark energy in the static world of galaxies and clusters of galaxies is gravitationally stable and can only oscillate by the influence of self-gravity. In the gravitational field of dark matter perturbations, it is able to condense monotonically, but the amplitude of density and velocity perturbations on all scales remains small. It was also illustrated that the “accretion” of phantom dark energy in the region of dark matter overdensities causes formation of dark energy underdensities-the regions with negative amplitude of density perturbations of dark energy.

Searching for the source of short-period comet nuclei: Choosing between different asteroid groups

Abstract: This study continues our previous works on searching for the main source of the nuclei of Jupiter family comets (JFCs). Angular orbit element distributions are analyzed for comets and asteroids of different groups. The distributions of JFCs by argument of perihelion ω and longitude of perihelion π are studied. The distributions are shown not to have been formed during the evolution of JFCs in their current orbits. Similar distributions N(ω) and N(π) are not observed in bodies that have come into the JFC orbits from external sources. At the same time, the distributions of JFCs by all angular orbit elements are very similar to those of the Trojans. It is concluded that the latter are likely to be the main source of the JFC nuclei.

Biographical index “Astronomers of Ukraine” at the UkrVO portal

Abstract: The new electronic database developed by the authors and titled “Astronomers of Ukraine” is described as a source of the main biographical data on astronomers of Ukraine from the 15th century until the beginning of the 21st century. The database is an upgrading component of the Ukrainian Virtual Observatory portal and contains the main biobibliographical data and papers concerning astronomers of Ukraine, as well as links to their publications. The existing biographical sources about astronomers in the world are discussed briefly. A list of the principal publications about astronomers of Ukraine is given.

Influence of magnetic field on propagation of five-minute oscillations in the sun’s atmosphere: Phase shifts

Abstract: From results of spectral (in Ba II λ 455.4-nm line) and spectropolarimetric (in Fe I λλ 1564.3–1565.8-nm lines) observations of the active region (an isolated faculae at the solar disk center) with the German vacuum tower telescope (VTT) at the Institute of Astrophysics on the Canary Islands, the peculiarities of propagation of five-minute oscillations from the photosphere base (h = 0 km) to the lower chromosphere (h = 650 km) were investigated. At the height of the continuum formation (h = 0 km), the nature of wave propagation in the active region does not differ much from that in the quiet region: 80–90% of the investigated areas are occupied by waves moving up and down. In the lower chromosphere (h = 650 km), differences in the behavior of the waves are fundamental. In a quiet area, the waves become standing for 90% of the cases. In contrast to this, in the presence of moderate and strong magnetic fields (B = 30–180 mT), in 47% of the cases, the waves are running upward, which gives the principal possibility to heat the active region. The investigations revealed the presence of the waves in the active region, for which the phase shift ΦT,V of the temperature and velocity oscillations is between −90° and 0°. These waves cannot propagate in a quiet atmosphere.

Preflare changes in the solar photosphere observed using the THEMIS telescope

Abstract: The physical state of the photosphere 1 h 50 min before a C1 solar flare on May 24, 2012, was studied. The spectropolarimetric data from the French-Italian THEMIS telescope (Tenerife Island, Spain) were used. The modeling was carried out through the inversion method using SIR [B. Ruiz Cobo and J. C. del Toro Iniesta, Astrophys. J. 398, 375–385 (1992)] code. Height distributions of temperature, magnetic field strength, and line-of-sight velocity were obtained. Nine semiempirical models of the photosphere were constructed. Each model has a two-component (a magnetic field component and nonmagnetic surroundings) structure. According to the obtained models, the magnetic field parameters and thermodynamic parameters did change significantly in the course of observations that lasted for 8 min. The models contain layers with increased and decreased temperature values. The magnetic field strength in these models varied, on average, from 0.2 T (lower photospheric layers) to 0.13 T (upper layers). The line-of-sight velocities did not exceed 2 km/s in lower and middle photospheric layers and rose to 5–6 km/s in the upper layers. The differences in the physical state and its changes occurring at different sites within the active region prior to the flare were revealed.