IIA Institutional Repository

Browsing by Author "Hasan, S. S"

Browsing by Author "Hasan, S. S"

Sort by: Order: Results:

  • The influence of magnetic fields on radiative damping of magnetoatmospheric oscillations 
    Banerjee, D; Hasan, S. S; Christensen-Dalsgaard, J (International Astronomical Union, 1998)
    We examine the non adiabatic effects on the modes of an isothermal stratified magnetic atmosphere. The present investigation is a continuation of earlier work by Banerjee, Hasan & Christensen-Dalsgaard (1995, 1996, 1997), ...
  • The Influence of Magnetic Flux Tubes on Their Environment 
    Hasan, S. S; Kalkofen, W (Astronomical Society of the Pacific, 1998)
    We present new calculations for model atmospheres in magnetic flux tubes extending vertically through the photosphere and convection zone of the Sun. This study is a continuation of earlier work by Hasan & Kalkofen (1994) ...
  • The influence of radiative damping on the modes of a magnetized isothermal atmosphere 
    Banerjee, D; Hasan, S. S; Christensen-Dalsgaard, J (Kluwer Academic Publishers, 1997)
    We examine the influence of radiative damping on the modes of an isothermal magnetized plasma. This investigation is an extension of earlier work by Hasan & Christensen-Dalsgaard (1992) and Banerjee, Hasan & Christens ...
  • Intense maganetic fields in the atmosphere of the sun 
    Hasan, S. S (Anita Publications, 2005)
  • Intensity oscillation in the corona as observed during the Total Solar Eclipse of 29 March 2006 
    Singh, J; Hasan, S. S; Gupta, G. R; Banerjee, D; Muneer, S; Raju, K. P; Bagare, S. P; Srinivasan, R (Springer, 2009-11)
    We obtained the images of the eastern part of the solar corona in the Fe xiv 530.3 nm (green) and Fe x 637.4 nm (red) coronal emission lines during the total solar eclipse of 29 March 2006 at Manavgat, Antalya, Turkey. ...
  • Kink and Longitudinal Oscillations in the Magnetic Network on the Sun: Nonlinear Effects and Mode Transformation 
    Hasan, S. S; Kalkofen, W; van Ballegooijen, A. A; Ulmschneider, P (The American Astronomical Society, 2003-03)
    We examine the propagation of kink and longitudinal waves in the solar magnetic network. Previously, we investigated the excitation of network oscillations in vertical magnetic flux tubes through buffeting by granules and ...
  • The Linear Response of a Magnetic Flux Tube to Buffeting by External p-Modes. I 
    Hasan, S. S (The American Astronomical Society, 1997-05)
    The linear response of a thin vertical magnetic flux tube to buffeting by p-modes in the ambient atmosphere is examined with the aim of understanding the interaction of acoustic modes with sausage tube waves. The idealized ...
  • Magnetic flux tubes and activity on the sun 
    Hasan, S. S (Springer, 2003)
    Activity on the Sun is associated with magnetic fields, involving a complex interaction between the field and plasma. In this review I focus on three fundamental aspects of magnetic activity: (a) the generation, storage ...
  • A magneto-hydrodynamic study of pre-flare loops 
    Hasan, S. S (Institute of Theoretical Astrophysics, 1979)
    The magnetohydrodynamic equilibrium and stability of a configuration which may apply to solar pre-flare loops is analyzed based on the following scenario: (1) the loops exist much prior to the flare and in equilibrium with ...
  • Magnetoatmospheric oscillations in sunspot umbrae 
    Hasan, S. S (The American Astronomical Society, 1990-01)
    The nature of umbral oscillations is investigated using an empirical model for the sunspot umbra, based on the model of Maltby et al. (1986). Approximating the sunspot as a thick flux tube of circular cross section, the ...
  • Magnetohydrodynamic equilibrium and stability of pre-flare loops - Constant pitch field 
    Hasan, S. S (D. Reidel Publishing Co.,, 1980-08)
    The equilibrium and stability of a loop in which energy storage occurs prior to a solar flare is discussed. Working on the hypothesis, that the onset of the flare begins only after sufficient magnetic energy has been stored ...
  • Magnetohydrostatic equilibrium in starspots: dependences on color (Teff) and surface gravity (g) 
    Rajaguru, S. P; Hasan, S. S (Cambridge University Press, 2011-08)
    Temperature contrasts and magnetic field strengths of sunspot umbrae broadly follow the thermal-magnetic relationship obtained from magnetohydrostatic equilibrium. Using a compilation of recent observations, especially in ...
  • MHD waves on the Sun 
    Hasan, S. S (Indian Association for the Cultivation of Science, 1992)
    Theoretical aspects of wave propagation in an atmosphere with a vertical magnetic field are reviewed. Starting from the ideal magneto hydrodynamic equations. The differential equations governing linear oscillations presented ...
  • Mode classification and wave propagation in a magnetically structured medium 
    Hasan, S. S; Sobouti, Y (Blackwell, 1987-09)
    The authors examine the structure of motions that can occur in a vertical magnetic flux tube with a rectangular cross-section. A polytropic stratification is assumed in the vertical direction. The authors use a gauged ...
  • Modelling sunspot equilibrium through a solution of the time dependent MHD equations 
    Gangadhara, R. T; Hasan, S. S (Astronomical Society of India, 1996)
    We numerically simulate the dynamical relaxation to equilibrium of a sunspot. Treating the sunspot as a thick axisymmetric flux tube in cylindrical geometry, we solve the time dependent MHD equation to examine the evolution ...
  • Modulation in the solar irradiance due to surface magnetism during cycles 21, 22 and 23 
    Jain, K; Hasan, S. S (EDP Sciences, 2004-10)
    Magnetic field indices derived from synoptic magnetograms of the Mt. Wilson Observatory, i.e. Magnetic Plage Strength Index (MPSI) and Mt. Wilson Sunspot Index (MWSI), are used to study the effects of surface magnetism on ...
  • 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 ...

Search DSpace

Browse

My Account