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Browsing by Author "Hasan, S. S"

Browsing by Author "Hasan, S. S"

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  • 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 ...
  • Solar astronomy at high altitude 
    Hasan, S. S; Bagare, S. P; Rangarajan, K. E (Indian National Science Academy, 2014-11)
    A major project called the National Large Solar Telescope (NLST) has been proposed for pursuing Solar Astronomy at High Altitude. The project envisages the development of a state-of-the-art 2-m class telescope to carry ...
  • Solar physics at the Kodaikanal observatory: a historical perspective 
    Hasan, S. S; Mallik, D. C. V; Bagare, S. P; Rajaguru, S. P (Springer, 2010)
    The Kodaikanal Observatory traces its origins to the East India Company, which started an observatory in Madras “for promoting the knowledge of astronomy, geography, and navigation in India.” Observations began in 1787 at ...
  • Solar physics in India: developments from the nineteenth century to the present era 
    Hasan, S. S; Choudhuri, A. R; Rajaguru, S. P (Astronomical Society of India, 2011)
    Modern solar astronomy took root in India with the discovery of helium during the total solar eclipse of 1868 and followed by the setting up of the Kodaikanal Observatory in 1899. We provide a brief overview of the growth ...
  • Spatial damping of compressional MHD waves in prominences 
    Singh, K. A. P; Dwivedi, B. N; Hasan, S. S (EDP Sciences, 2007-10)
    Aims.We study the spatial damping of linear compressional MHD waves in a homogeneous, isothermal, and unbounded prominence. Methods.We derive a general dispersion relation invoking the Newtonian radiation and turbulent ...
  • Spectral line radiation from solar small-scale flux tubes. II 
    Hasan, S. S; Kneer, F; Kalkofen, W (European Southern Observatory, 1998-04)
    We examine spectral line radiation from small-scale magnetic flux tubes in the solar atmosphere. This is a continuation of work by Kneer et al. (1996). The main difference with the previous investigation is in the choice ...
  • Spectral line radiation from solar small-scale magnetic flux tubes 
    Kneer, F; Hasan, S. S; Kalkofen, W (European Southern Observatory, 1996-01)
    We consider spectral line radiation from small-scale magnetic model flux tubes in the solar atmosphere. The structure of the tube is determined from the magnetostatic equations in the thin flux tube approximation. We assume ...
  • Spectropolarimetry with the NLST 
    Sankarasubramanian, K; Hasan, S. S; Rangarajan, K. E (Springer, 2010)
    India’s National Large Solar Telescope (NLST) will provide opportunities to observe the Sun with high spatial, spectral, and polarimetric resolution. The large aperture also enables high-cadence spectropolarimetry with ...
  • Spectroscopic Observation of Oscillations in the Corona During the Total Solar Eclipse of 22 July 2009 
    Singh, J; Hasan, S. S; Gupta, G. R; Nagaraju, K; Banerjee, D (Springer, 2011-05)
    We performed high resolution spectroscopy of the solar corona during the total solar eclipse of 22 July 2009 in two emission lines: the green line at 5303 Å due to Fe xiv and the red line at 6374 Å due to Fe x, simultaneously ...
  • Stability of cool flux tubes in the solar chromosphere Linear analysis 
    Hasan, S. S; Kneer, F (EDP Sciences, 1986-04)
    The linear stability of cool flux tubes in the solar chromosphere which are initially in radiative equilibrium is examined. Owing to the presence of carbon monoxide, there exists a narrow region near the temperature minimum ...
  • Stability of cool flux tubes in the solar chromosphere. II - Non-linear dynamical behaviour 
    Hasan, S. S; Kneer, F (The European Southern Observatory, 1990-06)
    A single vertical cool flux tube in the solar chromosphere is focused upon for stability studies. The analysis of a previous study by Hasan and Kneer (1986) is extended to the nonlinear regime with a view to examining the ...
  • Stokes Diagnostics of Magneto-Acoustic Wave Propagation in the Magnetic Network on the Sun 
    Vigeesh, G; Steiner, O; Hasan, S. S (Springer, 2011-10)
    The solar atmosphere is magnetically structured and highly dynamic. Owing to the dynamic nature of the regions in which the magnetic structures exist, waves can be excited in them. Numerical investigations of wave propagation ...
  • Structure of small-scale magnetic flux tubes and excitation of sausage mode oscillations 
    Hasan, S. S (Astronomical Society of India, 1998)
    The nature of small-scale magnetic fields in the solar atmosphere is discussed. In the first part of the review, equilibrium models for the structure of magnetic flux tubes are presented. It is shown that the thermodynamic ...
  • Three-dimensional simulations of magnetohydrodynamic waves in magnetized solar atmosphere 
    Vigeesh, G; Fedun, V; Hasan, S. S; Erdelyi, R (IOP Publishing, 2012-08-10)
    We present results of three-dimensional numerical simulations of magnetohydrodynamic (MHD) wave propagation in a solar magnetic flux tube. Our study aims at understanding the properties of a range of MHD wave modes generated ...
  • A time dependent model for spicule flow 
    Hasan, S. S; Venkatakrishnan, P (Kluwer Academic Publishers, 1981-09)
    A time dependent model for the flow of gas in a spicule is studied. In this model, the flow occurs in a magnetic flux sheath. Starting from hydrostatic equilibrium, the flux sheath is allowed to collapse normal to itself. ...
  • Time-dependent convective collapse of flux tubes 
    Hasan, S. S (D. Reidel Publishing Co, 1983)
    The time-dependent collapse of a slender flux tube extending vertically in the convection zone of the sun is modelled. Starting from an initial state in which the flux tube is in hydrostatic equilibrium, the non-linear MHD ...
  • Time-dependent interaction of granules with magnetic flux tubes 
    Venkatakrishnan, P; Hasan, S. S (Indian Academy of Sciences, 1981-06)
    The time-dependent interaction of the granulation velocity field with a magnetic flux tube is investigated here. It is seen that when a magnetic field line is displaced normal to itself so as to simulate thebuffeting action ...
  • Time-resolved spectral observations of spicule velocities at several heights 
    Hasan, S. S; Keil, S. L (American Astronomical Society, 1984-08)
    The vacuum telescope of the National Solar Observatory, Sacramento Peak was used to obtain H-alpha spectral observations of spicules. A set of spectra corresponding to five slit positions above the solar limb were recorded ...
  • Transient response of the solar wind to changes in flow geometry 
    Hasan, S. S; Venkatakrishnan, P (D.Reidel Publishing Co.,, 1982-10)
    An initial stationary flow in a configuration diverging as r-squared is assumed, a state corresponding to the normal solar wind solution. The effect on the flow through a tube whose area A(r, t) diverges faster than ...
  • Wave leakage in a magnetized isothermal atmosphere 
    Banerjee, D; Hasan, S. S; Christensen-Dalsgaard, J (Astronomical Society of India, 1996)
    The present investigation is a continuation of earlier work by Hasan & christensen-Dalsgaard (1992) and Banerjee, Hasan & Christensen-Dalsgaard(1995), where the interaction of various elementary modes in a stratified ...

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