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Browsing by Author "Krishan, V"

Browsing by Author "Krishan, V"

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  • Line formation in the Atmosphere of brown dwarf Gliese 229B : CH_4 at 2.3 mu m 
    Sengupta, S; Krishan, V (European Southern Observatory, 2000-06)
    We investigate the formation of methane line at 2.3 μm in Brown Dwarf Gliese 229B. Two sets of model parameters with (a) T_eff=940 K and log (g) =5.0, (b) T_eff=1030 K and log (g)=5.5 are adopted both of which provide ...
  • Magnetic field and the ionic tail of comet Halley 
    Krishan, V; Ramadurai, S (Astronomical Society of Indian, 1988-03)
    The space missions to comet Halley have reported an increase of the magnetic field from (12-15) x 10 to the -5th gauss, characteristic of the interplanetary solar wind, to a peak field strength of (70-80) x 10 to the -5th ...
  • Magnetic field generation from Alfven waves propagating along helical lines of force 
    Bera, B; Das, C; Chakraborty, B; Khan, M; Krishan, V; Bhattacharyya, B (Springer, 1992-07)
    A static induced magnetization of Alfven waves (IMAW) due to the inverse Faraday effect is defined and studied. The Alfven waves are assumed to propagate along helical lines of force of a force-free ambient magnetic field. ...
  • Magnetic fluctuations and Hall magnetohydrodynamic turbulence in the solar wind 
    Krishan, V; Mahajan, S. M (The American Geophysical Union, 2004-11)
    It is shown that the framework of Hall magnetohydrodynamics (Hall-MHD), which can support three quadratic invariants and allows nonlinear states to depart fundamentally from the Alfvénic, is capable of reproducing in the ...
  • Magnetic Helicity of Oscillating Coronal Loops 
    Krishan, V; Priest, E. R (International Astronomical Union, 1990)
  • Magnetic Transport on the Solar Atmosphere by Laminar and Turbulent Ambipolar Diffusion 
    Hiraki, Y; Krishan, V; Masuda, S (IOP Publishing, 2010-09-10)
    The lower solar atmosphere consists of partially ionized turbulent plasmas harboring velocity field, magnetic field, and current density fluctuations. The correlations among these small-scale fluctuations give rise to ...
  • Magnetic transport on the solar atmosphere by turbulent ambipolar diffusion 
    Krishan, V; Masuda, S (Anita Publications, 2008-12)
    The lower solar atmosphere consists of partially ionized turbulent plasmas harboring velocity field, magnetic field and current density fluctuations. The correlations amongst these small scale fluctuations give rise to ...
  • Magnetorotational instability in accretion disks 
    Krishan, V; Mahajan, S. M (Springer Netherlands, 2008)
    Accretion disks are a basic and an ubiquitous construct of nature. We describe their formation, briefly and qualitatively, in diverse astrophysical situations. These systems, though controlled by the gravitational forces, ...
  • Mean field solar surface dynamo in the presence of partially ionized plasmas and sub-surface shear layer 
    Paradkar, B. S; Chitre, S. M; Krishan, V (Oxford University Press on behalf of the Royal Astronomical Society, 2019-09)
    A non-linear α − Ω dynamo in the partially ionized turbulent plasma in the presence of sub-surface velocity shear is studied with mean-field electrodynamics. Such a dynamo is probably operational in the near-surface region ...
  • Mean-field dynamo in partially ionized plasmas – I 
    Krishan, V; Gangadhara, R. T (Blackwell Publishing, 2008-04)
    There are several astrophysical situations where one needs to study the dynamics of magnetic flux in partially ionized turbulent plasmas. In a partially ionized plasma, the magnetic induction is subjected to the ambipolar ...
  • Microflares in accretion disks 
    Krishan, V; Ramadurai, S; Wiita, P. J (The European Southern Observatory, 2003-02)
    We have investigated the phenomenon of explosive chromospheric evaporation from an accretion disk as a mechanism for fast variability in accreting sources such as low mass X-ray binaries and active galactic nuclei. This ...
  • Model for the relationship of granulation and supergranulation 
    Krishan, V (The University of Arizona Press, 1991)
    In this report a mechanism is proposed for producing the observed solar supergranulation from the photospheric granulation by a dissipative decay of two-dimensional turbulence, which leads to concentration of the energy ...
  • A model of solar granulation through inverse cascade 
    Krishan, V (Royal Astronomical Society, 1991-05)
    Nonlinear interactions between small fluid elements in an energetically open system facilitate the formation of large coherent stable structures. This is known as self-organization. Solar granulation on all scales is ...
  • Modeling of short scale turbulence in the solar wind 
    Krishan, V; Mahajan, S. M (European Geosciences Union, 2005-01)
    The solar wind serves as a laboratory for investigating magnetohydrodynamic turbulence under conditions irreproducible on the terra firma. Here we show that the frame work of Hall magnetohydrodynamics (HMHD), which can ...
  • Modelling of a solar coronal loop 
    Krishan, V (Cambridge University Press, 1996-12)
    Montgomery and co-workers have developed a framework to describe the steady state of a turbulent magnetofluid, without the usual recourse to linearization. Thus the magnetic and velocity fields emerge in their fully nonlinear ...
  • Modelling of Plasma Structures in the Solar Atmosphere 
    Krishan, V (Indian Institute of Astrophysics, Bangalore, 1984)
    A maximal helicity principle is proposed to study the stability of plasma structures in the solar atmosphere. This principle derives from the statistical treatment of the magnetohydrodynamical turbulence. The steady state ...
  • Modelling of Solar Coronal Oscillations 
    Krishan, V (Indian Institute of Astrophysics, Bangalore, 1997)
    The study of coronal osciallations is important since these oscillations could be responsible for the heating of the solar corona. Coronal structures are ex[ected to undergo three types of oscillations - non-compressional ...
  • Modelling rotation curves -- the turbulent way 
    Prabhu, R. D; Krishan, V (Astronomical Society of India, 1993)
    Helical hydrodynamic turbulence can magnify perturbation seed eddies and this can lead to the appearance of large scale structures. The evolution of the instability is accompanied by a transfer of energy from small scale ...
  • Models of Flux Tubes from Constrained Relaxation 
    Mangalam, A; Krishan, V (Indian Academy of Sciences, 2000-12)
    We study the relaxation of a compressible plasma to an equilibrium with flow. The constraints of conservation of mass, energy, angular momentum, cross-helicity and relative magnetic helicity are imposed. Equilibria ...
  • The modulation of radiation in an electron-positron plasma 
    Gangadhara, R. T; Krishan, V; Shukla, P. K (Royal Astronomical Society, 1993-05-01)
    The modulational instability of a large-amplitude, linearly polarized electromagnetic wave propagating in an electron-positron plasma is considered, including the combined effect of relativistic mass variation of the plasma ...

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