Hα, hard X-ray,and microwave emissions in the impulsive phase of solar flares

I have studied the observational relationship between the location of flare sites in active regions and three other observables, viz., H line width, hard X-ray burst parameters, and peak microwave fluxes. Results suggest that the strength of the magnetic field plays a role in governing the magnitudes of these emissions. Qualitative relationships are derived on the assumption of proportionality between the spectral maximum frequency of the associated microwave burst and the field strength in the microwave source.The relationship inferred between the power in thick target electrons (derived from the hard X-ray burst) and the column density of second-level hydrogen atoms (derived from the H line widths) is compared with calculations by Brown (1973) and Canfield (1974).The line widths observed for two white light flares suggest that a criterion for detectable continuum emission in disk flares is an H line width 20 Å.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

Analysis of the nonstationarity of the atmosphere of α Cyg. III. Variability of the Hα-line profile

The temporal variations of the radial velocity and profile of the Hα line in the spectrum of α Cyg are analyzed based on 240 CCD spectra taken with the coude spectrograph attached to the 2-m telescope of Shamaha Astrophysical Observatory of the National Academy of Sciences of Azerbaijan in 1998–2000. The results obtained are inconsistent with the conclusion made by the Heidelberg group concerning the behavior of the variability of the Hα-line profile [1]. The observed pattern of radial-velocity variations is due to nonradial pulsations and differs for the blue and red halves of the absorption profile. The pulsation parameters differ for different levels of residual intensity for both halves of the absorption profile. The amplitude and period increase from the core toward the wing of the line for the red half of the absorption profile, and, on the contrary, decrease toward the line wing for the blue half of the profile. Absorption features are observed on the blue half of the absorption profile. Their emergence and disappearance, as well as minor migrations are indicative of the clumpy structure of the stellar envelope. The similarity of the variability behavior of the absorption and emission profiles indicates that the latter too owe their variability to nonradial pulsations. Thus the variability of the stellar wind in its formation regions is partly due to the nonradial pulsations of the underlying layers of the atmosphere. On the whole, the variability of the position and photometric parameters of the absorption and emission components of the profile is indicative of the nonstationary nature and asymmetric shape of the stellar wind.     

A method of measuring the [α/Fe] ratios from the spectra of the LAMOST survey

The [α/Fe] ratios in stars are good tracers to probe the formation history of stellar populations and the chemical evolution of the Galaxy. The spectroscopic survey of LAMOST provides a good opportunity to determine [α/Fe] of millions of stars in the Galaxy. We present a method of measuring the [α/Fe]ratios from LAMOST spectra using the template-matching technique of the LSP3 pipeline. We use three test samples of stars selected from the ELODIE and MILES libraries, as well as the LEGUE survey to validate our method. Based on the test results, we conclude that our method is valid for measuring [α/Fe]from low-resolution spectra acquired by the LAMOST survey. Within the range of the stellar parameters Teff= [5000, 7500] K, log g = [1.0, 5.0] dex and [Fe/H]= [onsistent with values derived from high-resolution spectra,-1.5, +0.5] dex, our [α/Fe] measurements are c and the accuracy of our [α/Fe] measurements from LAMOST spectra is better than 0.1 dex with spectral signal-to-noise higher than 20.     

Observations of the Orion Nebula in Hα, [NII] and Hβ lines

Monochromatic photographs of the Orion Nebula taken through narrow bandpass interference filters (Δλ=10 Å) centred on Hα, Hβ and [NII] lines are presented. Ratio contours of Hα/[NII] and Hα/Hβ are derived. They enable a detailed study of the point-to-point variation in ionization structure and temperature throughout the nebula. Dust located within the ionized gas is studied from the Hα/Hβ ratio which varies from point to point over the nebula. Its strongest concentration, apart in the obvious ‘dark bay’, occurs in a shell surrounding the exciting stars, with about 2′ of diameter. Close to Θ¹ Ori the Hα/Hβ ratio, corrected for interstellar reddening, is about 3.0 in good agreement with the predicted value (Brocklehurst, 1971). To account for these measures, the following arguments are proposed:

1. Dust grains are completely or partially destroyed in region close to the exciting stars.
2. Radiation pressure and stellar wind push the remaining dust up to some equilibrium distance outwards. The consequence of this action is obviously the formation of a ‘dust mantle’ which is seen as a ring in projection.

     

Molecular dynamics estimates for the thermodynamic properties of the Fe–S liquid cores of the Moon,Io, Europa,and Ganymede

A molecular dynamics (MD) simulation is performed for the physical and chemical properties of solid and liquid Fe–S solutions using the embedded atom model (EAM) potential as applied to the internal structure of the Moon, Io, Europa, and Ganymede under the assumption that the satellites' cores can be described by a two-component iron–sulfur system. Calculated results are presented for the thermodynamic parameters including the caloric, thermal, and elastic properties (specific heat, thermal expansion, Grüneisen parameter, density, compression module, velocity of sound, and adiabatic gradient) of the Fe–S solutions at sulfur concentrations of 0–18 at %, temperatures of up to 2500 K, and pressures of up to 14 GPa. The velocity of sound, which increases as pressure rises, is weakly dependent on sulfur concentration and temperature. For the Moon’s outer Fe–S core (~5 GPa/2000 K), which contains 6–16 at % (3.5–10 wt %) sulfur, the density and the velocity of sound are estimated at 6.3–7.0 g/cm³ and 4000 ± 50 m/s, respectively. The MD calculations are compared with the interpretation of the Apollo observations (Weber et al., 2011) to show a good consistency of the velocity of P-waves in the Moon’s liquid core whereas the thermodynamic density of the Fe–S core is not consistent with the seismic models with ρ = 5.1–5.2 g/cm³ (Garcia et al., 2011; Weber et al., 2011). The revision the density values for the core leads to the revision of its size and mass. At sulfur concentrations of 3.5–10 wt %, the density of the Fe–S melt is 20–30% higher that the seismic density of the core. Therefore, the most likely radius of the Moon’s outer core must be less than 330 km (Weber et al., 2011) because, provided that the constraint on the Moon’s mass and moment of inertia is satisfied, an increase in the density of the core must lead to a reduction of its radius. For Jupiter’s Galilean moons Io, Europa, and Ganymede, constraints are obtained on the size, density, and sound velocity of the Fe–S liquid cores. The geophysical and geochemical characteristics of the internal structure of the Moon and Jupiter’s moons are compared. The calculations of the adiabatic gradient at the P–T conditions for the Fe–S cores of the Moon, Io, Europa, and Ganymede suggest the top-down crystallization of the core (Fe-snow scenario).     

Effects of the solar eclipse of August 1, 2008, on the earth’s lower atmosphere

The paper presents results of optical observations and analysis of dynamics of effects on the earth’s lower atmosphere of the partial solar eclipse (of magnitude 42%) of August 1, 2008, near Kharkov. This is compared with the effects induced by the partial solar eclipses on August 11, 1999, and October 3, 2005. All three eclipses occurred around midday. The standard deviation of the solar-limb displacement σ _S during the eclipses on October 3, 2005, August 1, 2008, and August 11, 1999, was established to decrease by 0.13, 0.30, and 0.68″ at the maximum of the solar obscuration function 0.13, 0.31, and 0.73, respectively, so that the temperature drop in the earth’s lower atmosphere t _a was 1.3, 2.0, and 7.3 K. The time lags of decreases of σ _S and t _a was found to be 15 and 5 minutes.     

On the value of 'αAR' from vector magnetograph data

This investigation centers upon the quantifying magnetic twist by the parameter , commonly defined as (×B_h)_z/B_z=₀J_z/B_z, and its derivation from vector magnetograph data. This parameter can be evaluated at each spatial point where the vector B is measured, but one may also calculate a single value of to describe the active region as a whole, here called '_AR'. We test three methods to calculate such a parameter, examine the influence of data noise on the results, and discuss the limitations associated with assigning such a quantity. The three methods discussed are (1) to parameterize the distribution of (x,y) using moments of its distribution, (2) to determine the slope of the function J_z(x,y)=_ARB_z(x,y) using a least-squares fit and (3) to determine the value of for which the horizontal field from a constant- force-free solution most closely matches the observed horizontal magnetic field. The results are qualitatively encouraging: between methods, the resulting value of the _ARparameter is often consistent to within the uncertainties, even though the resulting _ARcan differ in magnitude, and in some cases in sign as well. The worst discrepancies occur when a minimal noise threshold is adopted for the data. When the calculations are restricted to detections of 3 or better, there is, in fact, fair quantitative agreement between the three methods. Still, direct comparison of different active regions using disparate methods must be carried out with caution. The discrepancies, agreements, and overall robustness of the different methods are discussed. The effects of instrumental limitations (spatial resolution and a restricted field-of-view) on an active-region _AR, and quantifying the validity of _AR, are addressed in Paper II (Leka, 1999).     

On the value of 'αAR' from Vector Magnetograph data

This investigation is the second of two centering on the parameter =(×B_h)_z/B_z=₀J_z/B_zand its derivation from photospheric vector magnetogram data. While can be evaluated at every spatial position where the vector B is measured, for many reasons it is useful to determine a single value of to parameterize the magnetic complexity of an entire active region, here called _AR(see Leka and Skumanich, 1999). As such, the limitations in today's vector magnetograph data, e.g., finite spatial resolution and limited field of view, may influence any final '_AR' value. We apply three methods of calculating '_AR' to degraded high-spatial-resolution data and find that in general the discrepancies worsen for decreasing resolution compared to the original. We apply the three methods to sub-regions centered on the constituent sunspots for AR 7815. Two of the sub-regions are shown to have magnetic twist with significant magnitude but opposite sign. We show by mosaicing or otherwise combining separate sunspot observations that a measure of _ARcan be calculated which is consistent with a single large field-of-view observation. Still, the _AR0 assigned for the entire active region is an average, and does not accurately represent the magnetic morphology of this flux system. To measure the validity of the _ARparameterization, we demonstrate that, from each method, a relevant quantity can be calculated which describes the 'goodness of fit' of the resulting _AR. Given the spatial variation of (x,y) over an active region, it is suggested that such a second parameter be used either to indicate uncertainty in _ARor as a criterion for data selection, as appropriate.     

Diurnal variation of the linear polarization across the Hβ Fraunhofer line of the terrestrial atmosphere,I

When spectra of the daytime sky are compared with those directly from the Sun, it is found that the depths of the Fraunhofer lines are reduced. This indicates the presence of an added light, the Ring effect. Most previous research on the Ring effect has been performed spectroscopically, with the notion that the added component is always unpolarized. Here we presented spectropolarimetric observations using the principle of the line depth method (compression between the line centre and its continuum) to investigate this effect. The general scattered light of the blue sky is polarized and as the additional component may or may not also be polarized, the filling-in effect should be detectable by performing spectropolarimetry, which indeed has been achieved. The observations have involved the use of high precision polarimetry with spectral resolution 2 Å at the H Fraunhofer spectral line. The data indicate a variation of the linear polarization in the H line centre as a function of the solar zenith angle. One possible advantage of the polarimetric technique is that the Ring effect detections can be made without recourse to solar measurements directly or indirectly using an attenuator. Finally, a model without knowledge of the filling-in mechanism, has yielded a good qualitative agreement with the observational behaviours and it can be taken as a first step to explain the variation of the linear polarization across the spectral line.     

The results of the photographic positional observations of Venus on the wide-field astrograph of the Sternberg Astronomical Institute,Moscow State University,in 1969–1988

A new technique for the reduction of the observed position of Venus with a correction for the phase effect and photographic irradiation is briefly described. For the first time, a method for bringing the observed position of Venus into the system of standard exposure is proposed that considerably diminishes the random errors of a session and the whole line of observations. Original Venus observational material is presented together with accuracy estimations. The O-C difference yielded by the reduction procedure is plotted along both coordinate axes.     

Temperature Response of the 171 Å Passband of the SWAP Imager on PROBA2, with a Comparison to TRACE, SOHO, STEREO, and SDO

We calculated the temperature response of the 171 Å passbands of the Sun Watcher using APS detectors and image Processing (SWAP) instrument onboard the PRoject for OnBoard Autonomy 2 (PROBA2) satellite. These results were compared to the temperature responses of the Extreme Ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO), the Transition Region and Coronal Explorer (TRACE), the twin Extreme Ultraviolet Imagers (EUVI) onboard the Solar TErrestrial RElations Observatory (STEREO) A and B spacecraft, and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Multiplying the wavelength-response functions for each instrument by a series of isothermal synthetic spectra and integrating over the range 165?–?195 Å produced temperature-response functions for the six instruments. Each temperature response was then multiplied by sample differential emission-measure functions for four different solar conditions. For any given plasma condition (e.g. quiet Sun, active region), it was found that the overall variation with temperature agreed remarkably well across the six instruments, although the wavelength responses for each instrument have some distinctly different features. Deviations were observed, however, when we compared the response of any one instrument to different solar conditions, particularly for the case of solar flares.     

A Comparison of Solar Cycle Variations in the Equatorial Rotation Rates of the Sun’s Subsurface, Surface, Corona, and Sunspot Groups

Using the Solar Optical Observing Network (SOON) sunspot-group data for the period 1985?–?2010, the variations in the annual mean equatorial-rotation rates of the sunspot groups are determined and compared with the known variations in the solar equatorial-rotation rates determined from the following data: i) the plasma rotation rates at 0.94R_⊙,0.95R_⊙,…,1.0R_⊙ measured by the Global Oscillation Network Group (GONG) during the period 1995?–?2010, ii) the data on the soft-X-ray corona determined from Yohkoh/SXT full-disk images for the years 1992?–?2001, iii) the data on small bright coronal structures (SBCS) that were traced in Solar and Heliospheric Observatory (SOHO)/EIT images during the period 1998?–?2006, and iv) the Mount Wilson Doppler-velocity measurements during the period 1986?–?2007. A large portion (up to ≈?30^° latitude) of the mean differential-rotation profile of the sunspot groups lies between those of the internal differential-rotation rates at 0.94R_⊙ and 0.98R_⊙. The variation in the yearly mean equatorial-rotation rate of the sunspot groups seems to be lagging behind that of the equatorial-rotation rate determined from the GONG measurements by one to two years. The amplitude of the GONG measurements is very small. The solar-cycle variation in the equatorial-rotation rate of the solar corona closely matches that determined from the sunspot-group data. The variation in the equatorial-rotation rate determined from the Mount Wilson Doppler-velocity data closely resembles the corresponding variation in the equatorial-rotation rate determined from the sunspot-group data that included the values of the abnormal angular motions (>?|3^°|?day^?1) of the sunspot groups. Implications of these results are pointed out.     

Orbit and physical characteristics of the components of the massive Algol V622 Per,a member of the open star cluster χ Per

Analysis of the radial velocities based on spectra of high (near the H _α line) and moderate (4420–4960 Å) resolutions supplemented by the published radial velocities has revealed the binarity of a bright member of the young open star cluster χ Per, the star V622 Per. The derived orbital elements of the binary show that the lines of both components are seen in its spectrum, the orbital period is 5.2 days, and the binary is in the phase of active mass exchange. The photometric variability of the star is caused by the ellipsoidal shape of its components. Analysis of the spectroscopic and photometric variabilities has allowed the absolute parameters of the binary’s orbit and its components to be found. V622 Per is shown to be a classical Algol with moderate mass exchange in the binary. Mass transfer occurs from the less massive (\({M_1} = 9.1 \pm 2.7{M_ \odot }\)) but brighter (\(\log {L_1} = 4.52 \pm 0.10{L_ \odot }\)) component onto the more massive (\({M_2} = 13.0 \pm 3.5{M_ \odot }\)) and less bright (\(\log {L_2} = 3.96 \pm 0.10{L_ \odot }\)) component. Analysis of the spectra has confirmed an appreciable overabundance of CNO-cycle products in the atmosphere of the primary component. Comparison of the positions of the binary’s components on the T _eff–log g diagram with the age of the cluster χ Per points to a possible delay in the evolution of the primary component due to mass loss by no more than 1–2Myr.     

Meta-analysis from different tracers of the small Local Arm around the Sun—extent,shape, pitch,origin

The Sun in not located in a major spiral arm, and sits in a small ‘Local Arm’ (variously called arm, armlet, blob, branch, bridge, feather, finger, segment, spur, sub-arm, swath, etc.). The diversity of names for the ‘Local Arm’ near the Sun indicates an uncertainty about its shape or pitch or its extent from the Sun in each galactic quadrant, as well as an uncertainty about its origin.Here we extract data about the small ‘Local Arm’ near the Sun, from the recent observational literature, over many arm tracers, and we use statistics in order to find the local arm’s mean extent from the Sun, its possible shape and pitch angle from the direction of galactic longitude \(90^{\circ}\). Employing all tracers, the Local Arm is about 4 kpc long by 2 kpc large. The Sun is within 1 kpc of the center of the local arm. Proposed ‘bridges’ and ‘fingers’ are assessed. These bridges to nearby spiral arms and fingers across spiral arms may not reach the nearest spiral arms, owing to kinematic and photometric distance effects.We then compare these statistical results with some predictions from recent models proposed to explain the local arm (perturbations, resonances, density wave, halo supercloud, debris trail from a dwarf galaxy).The least controversial models involve importing materials from elsewhere (halo supercloud, debris trail) as a first step, and to be later deformed in a second step (by the Galaxy’s differential rotation into become roughly parallel to spiral arms) and then subjected to ongoing forces (global density waves, local perturbations).     

Identification of absorption lines of rare-earth elements in the region of the spectrum λλ 610.25–610.57 nm roAp stars,HD 101065, HD 134214, HD 137949, and HD 24712

In the spectral region λλ = 610.25−610.57 nm of the roAp star HD 101065, we performed the identification of the rare-earth element absorption lines absent from the atomic spectral line databases VALD and DREAM. The identified lines were used for calculating the synthetic spectra of the roAp stars HD 137949, HD 134214, and HD 24712. The upper limit of the identified line estimates was determined. The rotation/pulsation parameter νsini and magnetic field modulus were determined using the lines Nd III 669.083 nm and Ca I 616.217 nm. The element abundance in the roAp stars HD 134214 and HD 24712 was determined for the first time using Nd III lines. Calculations were carried out with the help of the code SynthM developed by S.A. Khan.     

Features of the Dynamics of Objects Moving in the Zones of Orbital Resonances 1 : 4, 1 : 6, and 1 : 8 with the Earth’s Rotation

Solar System Research - The paper presents the results of studying the dynamic structure of near-Earth orbital space in the regions of orbital resonances 1 : 4, 1 : 6, and 1 : 8 with the speed of...