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Browsing by Author "Hasan, S. S"

Browsing by Author "Hasan, S. S"

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  • National Large Solar Telescope of India 
    Hasan, S. S (Astronomical Society of India, 2011)
    The National Large Solar Telescope NLST will be a state-ofthe- art 2-m class telescope for carrying out high-resolution studies of the solar atmosphere. Sites in the Himalayan region at altitudes greater than 4000-m ...
  • NLST: India's National Large Solar Telescope 
    Hasan, S. S; Soltau, D; Kärcher, H; Süß, M; Berkefeld, T (Wiley-Blackwell, 2010-06)
    This article introduces the new Indian 2 m telescope which has been designed by MT Mechatronics in a detailed conceptual design study for the Indian Institute of Astrophysics, Bangalore. We describe the background of the ...
  • NLST: the Indian National Large Solar Telescope 
    Hasan, S. S; Soltau, D; Kärcher, H; Süss, M; Berkefeld, T (SPIE-The International Society for Optical Engineering, 2010-07)
    India is planning a new solar telescope with an aperture of 2-m for carrying out high resolution studies of the Sun. Site characterization is underway at high altitude locations in the Himalayan mountains. A detailed concept ...
  • Numerical Simulation of Wave Propagation in Magnetic Network 
    Vigeesh, G; Hasan, S. S; Steiner, O (Cambridge University Press, 2009-03)
    We present 2-D numerical simulations of wave propagation in the magnetic network. The network is modelled as consisting of individual magnetic flux sheets located in intergranular lanes. They have a typical horizontal size ...
  • Observations and Modeling of the Emerging Extreme-Ultraviolet Loops in the Quiet Sun as Seen With the Solar Dynamics Observatory 
    Pradeep Chitta, L; Kariyappa, R; Van Ballegooijen, A. A; DeLuca, E. E; Hasan, S. S; Hanslmeier, A (IOP Publishing, 2013-05-01)
    We used data from the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) to study coronal loops at small scales, emerging in the quiet Sun. With HMI ...
  • On the interchange instability of solar magnetic flux tubes. II. The influence of energy transport effects 
    Bunte, M; Hasan, S. S; Kalkofen, W (European Southern Observatory, 1993-06)
    We examine the interchange instability of thin photospheric magnetic flux tube models which satisfy both force and energy balance with their surroundings. The stability of the tubes is independent of the efficiency of ...
  • Oscillatory motions in intense flux tubes 
    Hasan, S. S (Royal Astronomical Society, 1986-03)
    The intricate nature of oscillatory motions in intene flux tubes is examined and states in which the ratio of gas to magnetic pressure (Beta) is constant are considered. Results are presented for both polytropic and real ...
  • Overview of the Sun 
    Hasan, S. S (World Scientific, 2008)
  • Photospheric Flow Fields and Properties of Embedded Small-scale Magnetic Flux Concentrations 
    Rajaguru, S. P; Srikanth, R; Hasan, S. S (Astronomical Society of the Pacific, 2001)
    The association between the different scales of convection on the solar photosphere and the field strengths/flux contents of discrete magnetic flux elements are analysed using simultaneously recorded SOHO MDI high resolution ...
  • Physics of Photospheric Magnetic Field 
    Van Ballegooijen, A. A; Hasan, S. S (Astronomical Society of the Pacific, 2003)
  • Probing the internal magnetic field of slowly pulsating B-stars through g modes 
    Hasan, S. S; Zahn, J. P; Christensen-Dalsgaard, J (EDP Sciences, 2005-12)
    Context: . Aims: .We suggest that high-order g modes can be used as a probe of the internal magnetic field of SPB (slowly pulsating B) stars. The idea is based on earlier work by the authors hich analytically investigated ...
  • Processes in the magnetized chromosphere of the Sun 
    Hasan, S. S (Cambridge University Press, 2009-03)
    We review physical processes in magnetized chromospheres on the Sun. In the quiet chromosphere, it is useful to distinguish between the magnetic network on the boundaries of supergranules, where strong magnetic fields are ...
  • Radial modes of rotating neutron stars in the Chandrasekhar-Friedman formalism 
    Datta, B; Hasan, S. S; Sahu, P. K; Prasanna, A. R (World Scientific Publishing Company, 1998-02)
    Eigenfrequencies of radial pulsations of "slowly" rotating neutron stars are calculated in a general relativistic formalism given by Chandrasekhar and Friedman (1972). It is found that the square of the frequencies are ...
  • Radiative Transfer Effects and Convective Collapse: Size(flux)-Strength Distribution for the Small-Scale Solar Magnetic Flux Tubes 
    Rajaguru, S. P; Hasan, S. S (Astronomical Society of the Pacific, 1999)
    The effects of radiative energy exchange on the convective instability of a weak field magnetic structure, which lead to a prediction and a physical explanation of the magnetic flux dependent field strength, are examined ...
  • Radiative Transfer Effects and the Dynamics of Small-Scale Magnetic Structures on the Sun 
    Rajaguru, S. P; Hasan, S. S (The American Astronomical Society, 2000-11)
    The dynamical consequences of radiative energy transport on the evolution of gas confined to small-scale magnetic structures on the Sun are studied. Convective collapse, which transforms weak-field structures into intense ...
  • Reconstruction of the past total solar irradiance on short timescales 
    Jain, K; Hasan, S. S (American Geophysical Union, 2004)
    The aim of this investigation is to present a new analysis of short-term variations in total solar irradiance by developing regression models and to extend these to epochs when irradiance measurements were not available. ...
  • Reconstruction of Total Solar Irradiance on Multiple Time Scales 
    Jain, K; Hasan, S. S (Astronomical Society of India, 2003)
    We have developed regression models of total solar irradiance on different time scales by parameterizing the combined influence of sunspots and faculae. These models are useful in identifying the key parameters responsible ...
  • Republication of: radial movement in sunspots 
    Hasan, S. S (Springer, 2010)
    Displacements of the lines of hydrogen and calcium in the neighbourhood of sunspots, indicating violent motions in the line of sight, is a common characteristic of spot disturbances. Such phenomena are frequently observed ...
  • Results from a revisit to the K2V bright points 
    Sivaraman, K. R; Gupta, S. S; Livingston, W. C; Damé, L; Kalkofen, W; Keller, C. U; Smartt, R; Hasan, S. S (European Southern Observatory, 2000-11)
    We have used pairs of temporally simultaneous CaII K-line spectroheliograms and magnetic area scans to search for spatial correlation between the CaII K2V bright points in the interior of the network and corresponding ...
  • Scientific Programmes with India's National Large Solar Telescope and their contribution to Prominence Research 
    Hasan, S. S (Cambridge University Press, 2014-01)
    The primary objective of the 2-m National Large Solar Telescope (NLST) is to study the solar atmosphere with high spatial and spectral resolution. With an innovative optical design, NLST is an on-axis Gregorian telescope ...

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