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Browsing by Subject "MHD"

Browsing by Subject "MHD"

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  • Alfvén-like mode in partially ionized solar atmosphere 
    Singh, K. A. P; Krishan, V (Elsevier, 2010-01)
    The partially ionized part of the solar atmosphere is investigated within the framework of a single-fluid magnetohydrodynamic (MHD) description including the non-ideal effects such as the Hall effect and the ambipolar ...
  • Constraints on dynamo action 
    Mangalam, A (Springer Netherlands, 2008)
    We discuss first geometrical constraints on dynamo action. Magnetic field decay is unavoidable under certain conditions of symmetry. These known results are encompassed by a calculation for flows described in terms of a ...
  • Decaying turbulence and magnetic fields in galaxy clusters 
    Sur, Sharanya (Oxford University Press on behalf of the Royal Astronomical Society, 2019-12)
    We explore the decay of turbulence and magnetic fields generated by fluctuation dynamo action in the context of galaxy clusters where such a decaying phase can occur in the aftermath of a major merger event. ...
  • Decaying turbulence and magnetic fields in galaxy clusters 
    Sur, Sharanya (Oxford University Press on behalf of the Royal Astronomical Society, 2019-09)
    We explore the decay of turbulence and magnetic fields generated by fluctuation dynamo action in the context of galaxy clusters where such a decaying phase can occur in the aftermath of a major merger event. Using idealized ...
  • Detection of high-frequency oscillations and damping from multi-slit spectroscopic observations of the corona 
    Samanta, T; Singh, J; Sindhuja, G; Banerjee, D (Springer, 2016-01)
    During the total solar eclipse of 11 July 2010, multi-slit spectroscopic observations of the solar corona were performed from Easter Island, Chile. To search for highfrequency waves, observations were taken at a high cadence ...
  • Dynamical Effects in Solar Photospheric Flux Tubes 
    Hasan, S. S (Kluwer Academic Publisher, 1996)
    The interaction of an intense flux tube, extending vertically through the photosphere, with p-modes in the ambient medium is modelled by solving the time dependent MHD equations in the thin flux tube approximation. It is ...
  • Dynamical Processes in Flux Tubes and their Role in Chromospheric Heating 
    Hasan, S. S (Indian Academy of Sciences, 2000-12)
    We model the dynamical interaction between magnetic flux tubes and granules in the solar photosphere which leads to the excitation of transverse (kink) and longitudinal (sausage) tube waves. The investigation is motivated ...
  • Effect of steady flow and Newton's cooling on the propagation and damping of small-amplitude prominence plasma oscillations 
    Singh, K. A. P; Dwivedi, B. N (Cambridge University Press, 2009-08)
    In study the propagation and damping of small-amplitude prominence oscillations invoking steady flow and radiative losses due to Newton's cooling with constant relaxation time. We find that the strength of steady flow has ...
  • Exact solution of the incompressible Hall magnetohydrodynamics 
    Mahajan, S. M; Krishan, V (Royal Astronomical Society, 2005-05)
    The Alfvén wave is known to be an exact solution of the ideal magnetohydrodynamics (MHD), and this has found use in modelling astrophysical turbulence. In this paper we show that the Hall MHD also submits itself to an exact ...
  • Faraday rotation signatures of fluctuation dynamos in young galaxies 
    Sur, Sharanya; Pallavi Bhat; Subramanian, K (Oxford University Press on behalf of the Royal Astronomical Society, 2018-03)
    Observations of Faraday rotation through high-redshift galaxies have revealed that they host coherent magnetic fields that are of comparable strengths to those observed in nearby galaxies. These fields could be generated ...
  • Inferring the chromospheric magnetic topology through waves 
    Hasan, S. S; Steiner, O; van Ballegooijen, A (Cambridge University Press, 2008-05)
    The aim of this work is to examine the hypothesis that the wave propagation time in the solar atmosphere can be used to infer the magnetic topography in the chromosphere as suggested by Finsterle et al. (2004). We do this ...
  • 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 ...
  • Kolmogorov dissipation scales in weakly ionized plasmas 
    Krishan, V; Yoshida, Z (Royal Astronomical Society, 2009-06)
    In a weakly ionized plasma, the evolution of the magnetic field is described by a `generalized Ohm's law' that includes the Hall effect and the ambipolar diffusion terms. These terms introduce additional spatial and ...
  • 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 ...
  • Non-radial Oscillations in an Axisymmetric MHD Incompressible Fluid 
    Satya Narayanan, A (Indian Academy of Sciences, 2000-12)
    It is well known from Helioseismology that the Sun exhibits oscillations on a global scale, most of which are non_radial in nature. These oscillations help us to get a clear picture of the internal structure of the Sun as ...
  • Occurrence of thermal instability in molecular clouds 
    Nejad-Asghar, M; Ghanbari, J (Astronomical Society of India, 2004-09)
    Linear perturbation is used on the complete MHD equations of the magnetic molecular clouds. We carry out a comparison of characteristic time-scales, and find conditions which linear thermal instability causes to form the ...
  • On the Rapid Variations of Solar Magnetic Fields 
    Venkatakrishnan, P; Kumar, B; Ravindra, B (Astronomical Society of India, 2003)
    We report on the rapid variations of solar magnetic fields that appear to be enhanced significantly above the background variability, at a few locations within the solar active regions, as observed with the Michelson Doppler ...
  • A probable initial configuration of a flaring loop 
    Krishan, V (Institute of Physics, 1986-02)
    A clue to the preflare configuration of a magnetic loop is obtained based on Taylor's hypothesis that the decay of energy to a minimum with magnetic helicity remaining constant leads to a force free state. The numerical ...
  • Properties of polarized synchrotron emission from fluctuation-dynamo action – I. application to galaxy clusters 
    Sur, Sharanya; Basu, Aritra; Subramanian, Kandaswamy (Oxford University Press on behalf of the Royal Astronomical Society, 2021-03)
    Using magnetohydrodynamic simulations of fluctuation dynamos, we perform broad-bandwidth synthetic observations to investigate the properties of polarized synchrotron emission and the role that Faraday rotation plays in ...
  • Quasi-periodic spicule-like cool jets driven by Alfvén pulses 
    Singh, B; Srivastava, A. K; Sharma, K; Mishra, S. K; Dwivedi, B. N (Oxford University Press on behalf of Royal Astronomical Society, 2022-04)
    We perform a 2.5D magnetohydrodynamic simulation to gain a comprehensive understanding of the formation of spicule-like cool jets caused by initial transverse velocity pulses akin to Alfven´ pulses in the solar chromosphere. ...

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