Radiation transfer in prominences with filamentary structure

Observations concerning the structure of sunspots, obtained during the fourth flight of the Soviet Stratospheric Observatory (SSO), are discussed. Objects brighter than the mean photospheric background inside the sunspot penumbra retaining the stable position sometimes vary within time intervals of a few minutes. The brightness change in pores can be explained by their different location at highest levels of the photosphere. The same mechanism can cause the brightness difference of the penumbra filaments. The gradient of the brightness variation inside the pores is determined. The value of this gradient was found to be practically the same for all dark objects. Most penumbral filaments show no magnetic expansion with growing distance from the spot center.     

Shadow mechanism and the opposition effect of brightness of atmosphereless celestial bodies

We consider the Irvine-Yanovistkii modification of the shadow model developed by Hapke for the opposition effect of brightness. The relation between the single scattering albedo ω and the transparency coefficient of particles κ is suggested to be used in the form κ = (1 ? ω) ⁿ , which allows the number of unknowns in the model to be reduced to two parameters (the packing density of particles g and ω) and the single-scattering phase function χ(α). The analysis of spectrophotometric measurements of the moon and Mars showed that the data on the observed opposition effect and the changes in the color index with the phase angle α well agree if the values of n = 0.25 and g = 0.4 (the moon) and 0.6 (Mars) are assumed in calculations. When being applied to asteroids of several types, this method also yielded a satisfactory agreement. For the E-type asteroids, the sets of parameters are [g = 0.6, ω = 0.6, A _g = 0.21, and q = 0.83] or [g = 0.3, ω = 0.4, A _g = 0.15, and q = 0.71] under the Martian single-scattering phase function; for the M-type asteroids, it is [g = 0.4, ω ≤ 0.1, A _g ≤ 0.075, and q ≤ 0.42] under the lunar single-scattering phase function; for the S-type asteroids, it is [g = 0.4, ω = 0.4, A _g = 0.28, and q = 0.49] under the lunar single-scattering phase function; and for the C-type asteroids, it is [g = 0.6, ω ≤ 0.1, A _g ≤ 0.075, and q = 0.43] under the modified lunar single-scattering phase function. The polarization measurements fulfilled by Gehrels et al. (1964) for the bright feature on the lunar surface, Copernicus (L = -20°08′, φ = +10°11′), at a phase angle α = 1.6° revealed the deviations in the position of the polarization plane from that typical for the negative branch. They were 22° and 12° in the G and I filters, respectively. At the same time, the deviation was within the error (±3°) in the U filter and for the dark feature Plato (L = -10°32′, φ = +51°25′), which can be caused by the coherent mechanism of the formation of the polarization peak.     

Aerosol in the upper layer of earth’s atmosphere

The upper atmospheric layer of Venus, Mars, Jupiter, Saturn, and earth contains an aerosol layer. The meteorites, rings, and removal of small planetary particles may be responsible for its appearance. The observations from 1979–1992 have shown that the optical aerosol thickness over the earth’s polar regions varies from τ ≈ 0.0002 to 0.1 to λ = 1 μm. The highest τ value was in 1984 and 1992 and was preceded by intense activity of the El Chichon (1982) and Pinatubo (1991) volcanoes. We have shown that increase in τ of the stratospheric aerosol may lead to decrease in ozone layer registered in the 1970s. The nature of the stratospheric aerosol (a real part of the refraction index), effective size particles r, and latitudinal variation τ remain unknown. The analysis of phase dependence of the degree of polarization is effective among the distal methods of determination of n _r and r. The observation value of intensity and degree of polarization in the visible light are caused by the optical surface properties and optical atmospheric thickness, whose values varied with latitude, longitude, and in time. Thus, it is impossible to correctly distinguish the contribution of the stratospheric aerosol. In UV-rays (λ < 300 nm), the ozone layer stops the influence of the surface and earth’s atmosphere up to height of 20–25 km. In this spectrum area, the negative factors are emission of various depolarizating gases, horizontal heterogeneity of the effective optical height of the ozone layer, and oriented particles indicated by variation of the polarization plane.     

A computer-aided framework for subsurface identification of white shark pigment patterns

Subsurface video footage can be used as a successful identification tool for various marine organisms; however, processing of such information has proven challenging. This study tests the use of automated software to assist with photo-identification of the great white shark Carcharodon carcharias in the region of Gansbaai, on the south coast of South Africa. A subsurface photo catalogue was created from underwater video footage. Single individuals were identified by using pigmentation patterns. From this catalogue, two images of the head for each individual were inserted into automated contour-recognition software (Interactive Individual Identification System Beta Contour 3.0). One image was used to search the database, the other served as a reference image. Identification was made by means of a contour, assigned using the software to the irregular border of grey and white on the shark's head. In total, 90 different contours were processed. The output provided ranks, where the first match would be a direct identification of the individual. The method proved to be accurate, in particular for high-quality images where 88.24% and 94.12%, respectively, were identified by two independent analysts as first match, and with all individuals identified within the top 10 matches. The inclusion of metadata improved accuracy and precision, allowing identification of even low-quality images.     

Dependence of the aerosol component of optical thickness and the relative concentration of methane on depth in atmospheres of giant planets

Based on the data on a spectral dependence of the geometric albedo of giant planet discs, we obtained depth variations in the optical thickness τ _a of the aerosol component and relative concentration γ of methane (Uranium, Neptune) lnτ _a = −0.720 + 1.507Δlnp (for −2.2085 ≤ lnp ≤ −1.0018), lnτ _a = +1.224 + 1.160Δlnp (for −1.0018 ≤ lnp ≤ −0.0595), lnτ _a = +2.318 + 0.192Δlnp (for −0.0595 ≤ lnp), γ = 0.0027 for Jupiter; lnτ _a = −0.846 + 1.598Δlnp (for −3.3619 ≤ lnp ≤ −2.0575), lnτ _a = +1.238 + 1.342Δlnp (for −2.0575 ≤ lnp ≤ −1.2074), lnτ _a = +2.379 + 0.722 (for −1.2074 ≤ lnp ≤ −0.6501), lnτ _a = +2.781 + 0.326Δlnp (for 0.6501 ≤ lnp), γ = 0.0027 for Saturn; lnτ _a = −2.694 + 0.087Δlnp (for +0.3685 ≤ lnp ≤ +1.2314), lnτ _a = −2.619 + 7.341Δlnp (for +1.2314 ≤ lnp ≤ +1.7556), lnτ _a = +1.229 + 0.956Δlnp (for +1.7556 ≤ lnp) for Uranium; lnτ _a = −1.861 + 1.248Δlnp (for +0.3204 ≤ lnp ≤ +0.9051), lnτ _a = −1.131 + 0.347Δlnp (for +0.9051 ≤ lnp) for Neptune; depth-averaged relative methane concentration lnγ = −9.982 + 2.676Δlnp(0.3584 ≤ lnp ≤ 1.5445); ln γ = −9.738 + 2.561Δlnp(0.3237 ≤ lnp ≤ 1.6156) and γ = 0.00382(lnp ≥ 1.6156); 0.00554(lnp ≥ 1.6156) for Uranium and Neptune, respectively (p is in bar).     

The optical properties of Venus and the Jovian planets I. The atmosphere of Jupiter according to polarimetric observations

Results are given for polarization measurements of both the entire Jupiter disk and its centre for seven wavelength regions in the 0.373–0.800 μm range. Interpretation of these observations is based on two model atmospheres: (A) The cloud layer particles and molecules are mixed with a constant ratio. (B) A gas layer with small optical thickness, τ₀, is situated above the cloud layer which consists of aerosol particles. The aerosol particles are considered to be non-absorbing spheres, their size distribution being normal Gaussian. The index of refraction for the particles is considered to be independent of wavelength in the above spectral range. An approximate method is used for the determination of parameters of the Jovian atmosphere. This method was tested by evaluation of the parameters for the Venus cloud layer: The refractive index was found to be n = 1.435 ± 0.015, the square of the logarithmic dispersion of the radius of particles σ² = 0.12 and the mean geometrical radius of particles r₀ = 0.74 μm which agree well with exact values given by Hansen and Arking (1971). For the atmosphere of Jupiter it was found: n = 1.36 ± 0.01, σ² ? 0.3, r₀ ? 0.2 μm. This refractive index for the particles agrees well with the ammonia cloud layer hypothesis.     

On the possibility of determining the imaginary part of the complex refractive index of aerosol particles in an individual altitudinal cloud layer of Jupiter’s atmosphere

We suggest the method for determining the imaginary part n _i of the complex refractive index of aerosol particles forming a cloud layer at a specified altitude in the atmosphere of a giant planet. From the data of spectral measurements of the geometric albedo of Jupiter (carried out in 1993), the value of n _i was calculated for the whole atmospheric column and the pressure range of 0.52 to 0.78 bar in the cloud layer presumably composed of ammon _i um hydrosulfides. The values of n _i obtained for the cloud layer and the whole atmospheric column substantially differ and amount to 0.00098 and 0.00012, respectively.     

On peculiarities of the H and K Ca ii lines of quiescent prominences

A study of the metallic lines in bright quiescent prominences indicates that the optical thickness in the K line of Ca ii may reach values as high as 10³. This is about 10 times larger than the optical thickness in the H line and may explain some peculiarities of the H and K lines in solar prominences.     

On the accuracy of indirect methods for estimating the sizes of asteroids

We have shown that the least reliable data source for estimating the albedo of asteroids is the maximal value of the degree of negative polarization. To increase the accuracy of the method that uses the data on the slope of the positive branch of polarization, the values of the approximating coefficient should be selected in accordance with a specified type of asteroids. The similar situation is in the shadow method, where the value of the phase integral q should be selected in accordance with each of the types. Moreover, the estimates obtained by both methods will be more reliable if the phase dependences of brightness that are characteristic of a specified type of asteroids, including the range of the opposition effect, are used in transforming from A(0) to A(α). The modeling performed with the Irvine-Yanovitskii modification of the shadow model of Hapke showed that the values of the phase coefficient β (10° ≤ α ≤ 20°) and q are, respectively, in the ranges of 0.016–0.030 and 0.6–1.0 for the E-type asteroids, 0.026–0.033 and 0.42–0.52 for the M-type asteroids, and 0.031–0.039 and 0.42–0.52 for the C-type asteroids.     

Ammonia in the atmospheres of Jupiter and Saturn: Absorption coefficients

Spectral values (with 1 nm spectral resolution) of the product of γk _ν and γ′k _ν (where k _ν is the monochromatic coefficient of ammonia absorption and γ and γ′ are the relative (with respect to 0.85/0.15 hydrogen-helium mixture and methane, respectively)) concentrations of ammonia for the absorption bands at λλ = 552, 604, 645, 787, and 932 nm in thermal conditions of Jupiter’s and Saturn’s atmospheres are determined ().