The characteristic size and brightness of facular points in the quiet photosphere

Using two very high resolution, white-light plates of the solar granulation, we measure a characteristic size and intensity for facular points. The plates were obtained with the 50 cm refractor at Pic-du-Midi Observatory using a 60 Å bandpass filter center at 5750 Å. After adjustment for atmospheric and instrumental smearing, we find a characteristic size of 0.22 arc sec and a characteristic intensity of 1.3 to 1.5 times the mean continuum intensity.NAS/NRC Resident Research Associate, on leave from Pic du Midi Observatory, France.Operated by the Association of Universities for Research in Astronomy, Inc., under contract AST 78-17292 with the National Science Foundation.     

Electrical conductivity in sunspots and the quiet photosphere

The electrical conductivity, thermal conductivity and viscosity of models of the quiet photosphere and the umbra of a sunspot have been calculated using LTE ionization equilibria and the Chapman-Enskog theory of transport coefficients. The results are presented in tabular form, and compared with previous calculations.     

Temperature variation with latitude in the upper solar photosphere: Relevance to solar oblateness measurements and facular models

Solar Physics - Altrock and Canfield's observations of temperature variation with latitude in the upper solar photosphere refer to higher levels (smaller optical depths) than those to which...     

Characterizing motion types of G-band bright points in the quiet Sun

We study the motion of G-band bright points(GBPs)in the quiet Sun to obtain the characteristics of different motion types.A high resolution image sequence taken with the Hinode/Solar Optical Telescope(SOT)is used,and GBPs are automatically tracked by segmenting 3D evolutional structures in a space-time cube.After putting the GBPs that do not move during their lifetimes aside,the non-stationary GBPs are categorized into three types based on an index of their motion type.Most GBPs that move in straight or nearly straight lines are categorized as a straight motion type,a few moving in rotary paths into rotary motion,and the others fall into a motion type we called erratic.The mean horizontal velocities are 2.18±0.08 km s-1,1.63±0.09 km s-1and 1.33±0.07 km s-1for straight,erratic and rotary motion types,respectively.We find that a GBP drifts at a higher and constant velocity during its whole life if it moves in a straight line.However,it has a lower and variational velocity if it moves on a rotary path.The diffusive process is ballistic-,super-and sub-diffusion for straight,erratic and rotary motion types,respectively.The corresponding diffusion index(γ)and coefficients(K)are 2.13±0.09 and 850±37 km2s-1,1.82±0.07 and331±24 km2s-1,and 0.73±0.19 and 13±9 km2s-1.In terms of direction of motion,it is homogeneous and isotropic,and usually persists between neighboring frames,no matter what motion type a GBP is classified as.     

The correspondence between x-ray bright points and evolving magnetic features in the quiet sun

Coronal bright points, first identified as X-ray Bright Points (XBPs), are compact, short-lived and associated with small-scale, opposite polarity magnetic flux features. Previous studies have yielded contradictory results suggesting that XBPs are either primarily a signature of emerging flux in the quiet Sun, or of the disappearance of pre-existing flux. With the goal of improving our understanding of the evolution of the quiet Sun magnetic field, we present results of a study of more recent data on XBPs and small-scale evolving magnetic structures. The coordinated data set consists of X-ray images obtained during rocket flights on 15 August and 11 December, 1987, full-disk magnetograms obtained at the National Solar Observatory - Kitt Peak, and time-lapse magnetograms of multiple fields obtained at Big Bear Solar Observatory. We find that XBPs were more frequently associated with pre-existing magnetic features of opposite polarity which appeared to be cancelling than with emerging or new flux regions. Most young, emerging regions were not associated with XBPs. However, some XBPs were associated with older ephemeral regions, some of which were cancelling with existing network or intranetwork poles. Nearly all of the XBPs corresponded to opposite polarity magnetic features which wereconverging towards each other; some of these had not yet begun cancelling. We suggest that most XBPs form when converging flow brings oppositely directed field lines together, leading to reconnection and heating of the newly-formed loops in the low corona.     

The potassium abundance in the solar photosphere

High precision center-limb spectrograms of the K i resonance doublet line at λ 7699 Å were used to study the line formation and to determine the abundance of potassium in the solar atmosphere. The LTE assumption is not valid for these lines. Synthetic profiles computed in NLTE reproduce very well the observed center-limb line behaviour and yield log? _K = 5.14±0.10 for the solar abundance of potassium (on the scale of log? _H = 12 for Hydrogen).     

Wave behavior in the solar photosphere: A comparison of theory and observation

We report detailed comparisons between theoretical and empirical eigenfunctions of velocity and intensity for the 5-min modes in the photosphere. The comparison process is accomplished by obtaining synthetic profiles of the Fei 5434 Å line in the presence of waveforms given by dynamical calculations and then applying a common procedure of reduction both to the observed and to the synthetic data. For the velocity waveforms, our results show a general agreement between theory and observations together with some systematic differences; in particular the theory systematically underestimates the observations in the low photosphere. These systematic differences are stressed by the intensity results since both the computed amplitudes and phases appear to be wrong in the deeper layers.     

Waves in the solar photosphere

Time-sequences of line profile data have been subjected to a unique analysis which produces an amplitude and phase of the velocity and intensity at several line depths for each time sample and spatial point on the Sun. The data have been filtered to pass only the frequencies and spatial wavenumbers of the 5-min band. Yet, a secondary oscillation emerges, the phase of which propagates downward. Empirical eigenfunctions for velocity and intensity are given, and the kinetic energy flux is computed.Operated by the Association of Universities for Research in Astronomy under contract with the National Science Foundation.     

Wave propagation in the photosphere

Using a 32 minutes sequence of observation, brightness and velocity fluctuations in the wings of the Mgi line at 5172.7 Å and Fe ii line at 5197.578 Å are analysed. The analysis of phase shifts and amplitude ratios leads to the following conclusions:

Visibility of facular fields in Mgi b-lines

On the basis of photoelectric observations, the center-to-limb variations of the brightness of restricted areas (≈0.5″ × 7.0″) of unresolved facular granules were determined at different frequencies in the lines λ5183 Å and λ5172 Å of Mgi. It was found that the chromospheric plages reach maximum intensity in the central parts of the lines at the same position on the solar disk where photospheric faculae have maximum brightness. The floccular emission is conspicuous in the cores of the lines up to a distance Δλ = 0.02 Å. In the portion of the lines corresponding to 0.02 Å < Δλ < 0.18 Å the contrast of flocculi decreases to a minimum value and then increases again in the inner wings of these lines. In the far wings the contrast of facular areas systematically decreases to the continuum values.     

Molecules in the solar photosphere

A consideration of the dissociation equilibrium of diatomic molecules in the Utrecht Reference Photosphere leads us to conclude that SH, SiO, CS, HF and HCl may show up in enough concentrations in the solar atmosphere. The number above photosphere for these molecules is comparable with or more than that of MgH.     

Inhomogeneities in the solar photosphere

A model of the solar photosphere incorporating a simple two-stream representation of granulation is found to give a small but significant improvement in the continuous radiation field over a homogeneous model. It is common to assume that the pressure does not vary with horizontal position; however, this assumption cannot be valid if the material is in hydrostatic equilibrium, so horizontal pressure differences between the hot and cold columns are allowed. This has a major effect on the structure, and one of the consequences is that temperature fluctuations at equal optical depths are greater than those at equal geometric depths.Now at Georgetown College Observatory, Washington, D.C., U.S.A.     

Statistical study of photospheric bright points in an active region and quiet Sun

Agegraphic dark energy (ADE) and New-ADE models have been introduced as two candidates for dark energy to explain the accelerated expansion phase of the Universe. In spite of a few suitable features of these models some studies have shown that there are several drawbacks in them. Therefore in this investigation a new version of ADE and New-ADE are studied which can improve such drawbacks appearing in the ordinary ADE and New-ADE scenario. In fact we consider an interacting model of scalar field with matter and after re-deriving some cosmological parameters of the model, we find out the best fit for the model. Actually by finding the best fitting for free parameters of the model, we show that our theoretical results are in a good agreement with observational data.     

The horizontal variation of temperature in the low solar photosphere

Observations of the rms intensity fluctuations in the continuum obtained by Pravdjuk et al. (Solnechnye Dannye, No. 2, p. 70, 1974) from white-light photographs made with the Soviet Stratospheric Solar Observatory are analyzed to obtain a horizontal temperature-fluctuation amplitude as a function of depth. The results indicate that temperature fluctuations increase with depth monotonically from a small value at ₅₀₀₀0.5 (cf. Figure 2). The initial rise of T appears quite steep, having a slope of approximately 20 K km^–1. The model of Wilson (Solar Phys. 9, 303, 1969) is incompatible with the data. Convective flux in the present model is approximately 6% of the total flux at ₅₀₀₀ = 1.     

The empirical determination of damping constants in the solar photosphere

We determine empirical damping constants for 73 selected Fe i lines following the method of Gurtovenko and Kondrashova (1980), employing high-quality observations and the accurate list of Fe i oscillator strengths by Gurtovenko and Kostik (1980).The results show: (i) No increase of the enhancement factor to van der Waals broadening with excitation potential, as predicted by Edmunds (1975), and with the frequency of the transition (Figure 1); (ii) a substantial part of the commonly-used enhancement factor for weaker lines is not due to collisional damping (Figure 2), but to a misrepresentation of the inhomogeneous structure of the deep photosphere. This false damping effect is not seen in the stronger lines which yield an average damping constant : 1.3₆ 1.5 ₆.     

The empirical determination of damping constants in the solar photosphere

The evaluation of damping constants is discussed and the results of their empirical determination by various authors are listed in the Appendix.The results of the determination of damping constants by analysing the wings of 38 strong Fe i lines are discussed and compared with previous results obtained by the same method from 27 moderate Fe i lines.The van der Waals damping constant ₆ multiplied by an enhancement factor E = 2.5 is suggested for the interpretation of Fe i Fraunhofer lines.     

Temperature variations in the solar photosphere

From the variations in equivalent width of a selected set of Fraunhofer lines, we derived the variation of effective temperature and microturbulence velocity between the equator and the regions at heliographic latitude of - 72°. The reliability of the results (T/T = 0 ± 0.6%, / = 6% ± 13%) needs further investigations, but from the analysis of our data we can state that temperature variations, if any, are very small. Some suggestions for more fruitful measurements are also given.