• Issue front cover thumbnail

      Volume 29, Issue 3-4

      September 2008,   pages  363-414

    • Error Minimization of Polynomial Approximation of Delta 𝑇

      Islam Sana Sadiq Muhammad Qureshi Muhammad Shahid

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      The difference between Universal time (UT) and Dynamical time (TD), known as Delta 𝑇(𝛥 𝑇) is tabulated for the first day of each year in the Astronomical Almanac. During the last four centuries it is found that there are large differences between its values for two consecutive years. Polynomial approximations have been developed to obtain the values of 𝛥 𝑇 for any time of a year for the period AD 1620 to AD 2000 (Meeu 2000) as no dynamical theories describe the variations in 𝛥 𝑇. In this work, a new set of polynomials for 𝛥 𝑇 is obtained for the period AD 1620 to AD 2007 that is found to produce better results compared to previous attempts.

    • Investigation of the Effects of Expectation Values for Radii on the Determination of Transition Probabilities using WBEPM Theory

      Gültekin Çelik Şule Ateş

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      Transition probabilities for some excited s–p and p–s transition arrays of neutral nitrogen have been calculated using the weakest bound electron potential model theory (WBEPMT) for the investigation of effects of expectation values of radii.We have used both numerical non-relativistic Hartree-Fock (NRHF) wave functions and numerical Coulomb approximation (NCA) wave functions to calculate expectation values of radii. The transition probability results obtained using the parameters determined with two different wave functions agree well with each other and accepted values taken from NIST for low values of transition probability. However, the NRHF wave functions present better results for p–s transitions, while NCA wave functions are better in s–p transitions for large values of transition probability.

    • Gravitation Field Dynamics in Jeans Theory

      A. A. Stupka

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      Closed system of time equations for nonrelativistic gravitation field and hydrodynamic medium was obtained by taking into account binary correlations of the field, which is the generalization of Jeans theory. Distribution function of the systemwas built on the basis of the Bogolyubov reduced description method. Calculations were carried out up to the first order of a perturbation theory in interaction. Adiabatic and enthropic types of perturbations were corrected and two new types of perturbations were found.

    • Observational Evidences for Multi-component Magnetic Field Structure in Solar Flares

      V. G. Lozitsky J. Staude

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      Two solar flares of 25 July 1981 and 5 November 2004 of importance 2𝑁 and M4.1/1B, respectively, were investigated using observational data obtained with the Echelle spectrograph of the Kyiv University Astronomical Observatory. Stokes 𝐼 and 𝑉 profiles of the FeI lines 5233, 5247.1, 5250.2, 5250.6, 5576.1 and of CrI 5247.6 Å have been analyzed. We found several evidences for the existence of spatially unresolved magnetic field structures with kG strengths. In particular, the values of the measured average longitudinal field 𝐵 depend on the Lande factors 𝑔 of the lines: in general, 𝐵 increases with increasing factor 𝑔. Analogously, the observed line ratio 𝐵 (5250.2)/𝐵(5247.1) is increasing with increasing distance 𝛥 𝛾 from the line center. The observed Stokes 𝑉 profiles show some deviations from that of an assumed homogeneous field, presented by the Stokes 𝐼 gradient, 𝑑𝐼/𝑑𝛾. A comparison with the non-split line FeI 5576.1 Å shows that some of these deviations are real and indicate the presence of subtelescopic magnetic elements with discrete field strengths of several kG. The lines with large Lande factors have considerable broadenings of the Stokes 𝐼 profiles, indicating a strong background magnetic field of mixed polarity. On the basis of all these data we conclude that a four-component magnetic field structure is a possible explanation. The field strengths are about ±1.05 kG in the background field, and 1.3–1.5, 3.9–4.0, and 7.4–7.8 kG at level of middle photosphere (ℎ ≈ 300 km) in the spatially unresolved, small-scale magnetic elements.

    • Author Index

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    • Subject Index

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  • Journal of Astrophysics and Astronomy | News

    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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