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Browsing by Author "Hasan, S. S"

Browsing by Author "Hasan, S. S"

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  • 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 ...
  • Wave propagation and energy transport in the magnetic network of the Sun 
    Vigeesh, G; Hasan, S. S; Steiner, O (European Southern Observatory, 2009-12)
    Aims. We investigate wave propagation and energy transport in magnetic elements, which are representatives of small scale magnetic flux concentrations in the magnetic network on the Sun. This is a continuation of earlier ...
  • Wave propagation in multiple flux tubes and chromospheric heating 
    Hasan, S. S; van Ballegooijen, A; Steiner, O (Cambridge University Press, 2008-05)
    This investigation is a continuation of earlier work on the dynamics of the magnetic network. In a previous calculation (Hasan et al. 2005), we examined the response of a single flux tube to transverse motions of its ...
  • Wave propagation in sunspots 
    Hasan, S. S (International Astronomical Union, 1990)
    Wave propagation in sunspot umbrae is analyzed; the stratification in a typical umbra is approximated by a model atmosphere, extending vertically from a depth of a few thousand kilometers below the photosphere, to the ...
  • Wave propagation in the magnetic network on the Sun 
    Hasan, S. S; Vigeesh, G; van Ballegooijen, A. A (Cambridge University Press, 2006)
    Hasan et al. (2005) have recently presented 2-D dynamical calculations on wave propagation in in the magnetic network of the Sun. The latter is idealized as consisting of non-potential flux tubes in the quiet solar ...
  • Why Does the Sun Have Kilogauss Magnetic Fields? 
    Hasan, S. S; van Ballegooijen, A. A (Astronomical Society of the Pacific, 1998)
    Magnetic fields in the solar photosphere are concentrated in flux tubes with kilogauss field strength surrounded by nearly field-free plasma. Observations show that the flux tubes are located in convective downdrafts where ...

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