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    ABSTRACT: We report high angular resolution observations of the outer solar corona carried out at 75 MHz from the Gauribidanur Radio Observatory (Long: 77 degrees 26/12 " E, Lat: 13 degrees 36'12 " N) about 100 km north of Bangalore, India, during the solar eclipse of October 24, 1995. Our main conclusion is that there are structures of angular size less than or equal to 2.5' in the outer solar corona at a height of approximate to 0.4 R. above the photosphere. (C) 2000 COSPAR. Published by Elsevier Science Ltd.
    No preview · Article · Jul 2013 · Advances in Space Research
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    ABSTRACT: We present a detailed thermal and structural analysis of a 2m class solar telescope mirror which is subjected to a varying heat load at an observatory site. A 3-dimensional heat transfer model of the mirror takes into account the heating caused by a smooth and gradual increase of the solar flux during the day-time observations and cooling resulting from the exponentially decaying ambient temperature at night. The thermal and structural response of two competing materials for optical telescopes, namely Silicon Carbide – best known for excellent heat conductivity and Zerodur – preferred for its extremely low coefficient of thermal expansion, is investigated in detail. The insight gained from these simulations will provide a valuable input for devising an efficient and stable thermal control system for the primary mirror.
    No preview · Dataset · May 2013
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    ABSTRACT: Hanle scattering is an important diagnostic tool to study weak solar magnetic fields. Partial frequency redistribution (PRD) is necessary to interpret the linear polarization observed in strong resonance lines. Usually angle-averaged PRD functions are used to analyze linear polarization. However it is established that angle-dependent PRD functions are often necessary to interpret polarization profiles formed in the presence of weak magnetic fields. Our aim is to present an efficient decomposition technique, and the numerical method to solve the concerned angle-dependent line transfer problem. Together with the standard Stokes decomposition technique we employ Fourier expansion over the outgoing azimuth angle to express in a more convenient form, the angle-dependent PRD function for the Hanle effect. It allows the use of angle-dependent frequency domains of Bommier to solve the Hanle transfer problem. Such an approach is self-consistent and accurate compared to a recent approach where angle-averaged frequency domains were used to solve the same problem. We show that it is necessary to incorporate angle-dependent frequency domains instead of angle-averaged frequency domains to solve the Hanle transfer problem accurately, especially for the Stokes U parameter. The importance of using angle-dependent domains has been highlighted by taking the example of Hanle effect in the case of line transfer with vertical magnetic fields in a slab atmosphere. We have also studied the case of polarized line formation when micro-turbulent magnetic fields are present. The difference between angle-averaged and angle-dependent solutions is enhanced by the presence of micro-turbulent fields.
    Full-text · Article · Apr 2013 · Journal of Quantitative Spectroscopy and Radiative Transfer


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Planetary and Space Science 10/2013; 89. DOI:10.1016/j.pss.2013.08.022
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