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Browsing by Author "Venkatakrishnan, P"

Browsing by Author "Venkatakrishnan, P"

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  • The Kodaikanal solar vector magnetograph - Laboratory evaluation of the polarimeter 
    Venkatakrishnan, P; Narayanan, R. S (Astronomical Society of India, 1991)
    Laboratory experiments performance to evaluate the sensitivity of the polarimeter of the Kodaikanal vector magnetograph. The polarimeter does not produce significant cross talk and has a sensitivity of about 1 percent polarization
  • Loss of magnetic tension in pre-flare magnetic configurations 
    Venkatakrishnan, P (Kluwer Academic Publishers, 1990-08)
    We demonstrate that magnetic tension vanishes at regions of large magnetic shear on the polarity inversion line. The characteristics of these tension-free fields depend on the density of the medium and, therefore, change ...
  • Magnetic Shear and Flares 
    Venkatakrishnan, P (International Astronomical Union, 1990)
    Magnetic tension possesses low values at regions of large magnetic “shear” on the polarity inversion line. The low tension allows for a non-force-free field that depends on the density may then possibly evolve into solar ...
  • Measurement of instrumental polarisation of the Kodaikanal tunnel tower telescope 
    Sankarasubramanian, K; Samson, J. P. A; Venkatakrishnan, P (Kluwer Academic Publishers, 1999)
    The measurement of the instrumental polarization for any obliquely reflecting telescope is necessary to measure the polarization state of the input beam precisely. To find out the instrumental polarization of the reflecting ...
  • Measurement of vector magnetic fields. I - Theoretical approach to the instrumental polarisation of the Kodaikanal Solar Tower 
    Balasubramaniam, K. S; Venkatakrishnan, P; Bhattacharyya, J. C (D. Reidel Publishing Co., 1985-09)
    The observations of Stokes line profiles require an accurate knowledge of the instrumental polarisation caused by optical components in the path of the light beam. In this context we present a theoretical approach to the ...
  • Membrane-based deformable mirror: intrinsic aberrations and alignment issues 
    Bayanna, A. R; Louis, R. E; Chatterjee, S; Mathew, S. K; Venkatakrishnan, P (Optical Society of America, 2015-03-01)
    A deformable mirror (DM) is an important component of an adaptive optics system. It is known that an on-axis spherical/parabolic optical component, placed at an angle to the incident beam introduces defocus as well as ...
  • MHD waves at a tangential discontinuity with inclined magnetic fields and flows 
    Satya Narayanan, A; Pandey, V; Venkatakrishnan, P (European Solar Physics, 2008-09)
    Propagation of magnetohydrodynamic (MHD) waves in inhomo- geneous magnetic plasmas is interesting from space and astrophysical point of view. In this study, the combined effect of non-parallel propagation, steady flow and ...
  • Morphology of Ca II K bright points and their link to G band bright points 
    Krishnakumar, V; Venkatakrishnan, P; Srikanth, R (Astronomical Society of India, 2000)
    We present the results of a preliminary analysis of a time series of a sequence of Ca II K bright points and G band bright points observed co-spatially and co-temporally. Inspection of these images shows that the larger ...
  • The Multi Application Solar Telescope 
    Venkatakrishnan, P; Mathew, S. K; Srivastava, N; Bayanna, A. R; Kumar, B; Ramya, B; Jain, N; Saradava, M (Current Science Association, 2017-08)
    Multi Application Solar Telescope (MAST), a telescope for the detailed study of solar activity, was operationalized at the Udaipur Solar Observatory (USO) of Physical Research Laboratory (PRL), on 16 June 2015. This ...
  • Multi-aperture solar telescope 
    Venkatakrishnan, P (Astronomical Society of India, 2001)
    A proposal for a new ground based solar telescope of very high angular resolution is presented. The science goals that drive the need for this facility are enumerated. The proposed strategy, of combining several smaller ...
  • Narrow Band Photometry in Emission Lines during the Total Solar Eclipse of October 24, 1995 
    Singh, J; Cowsik, R; Venkatakrishnan, P; Srinivasan, R; Chinnappan, V; Raju, K. P; Srikanth, R (Indian Institute of Astrophysics, Bangalore, 1997)
    To investigate the spatial variation of tempereture and density within coronal strucures, narrow band photometry in three coronal emission lines was done during this eclipse. The emission lines 6374 (FeX), 7892 (Fe XI) and ...
  • A New Technique for Solar Imaging Spectro-polarimetry using Shack-Hartmann and Fabry-Perot 
    Gosain, S; Sankarasubramanian, K; Venkatakrishnan, P; Bayanna, A. R (Astronomical Society of the Pacific, 2012-12)
    A new technique for solar imaging spectro-polarimetry is presented. Using the combination of a Shack-Hartmann (SH) and a Fabry-Pérot (FP) interferometer, high-cadence spectroscopic observations can be obtained at discrete ...
  • Nonlinear development of convective instability within slender flux tubes. I - Adiabatic flow 
    Venkatakrishnan, P (Indian Academy of Sciences, 1983-06)
    The nonlinear development of convective instability within slender flux tubes is studied using the method of characteristics. It is seen that the initial magnetic field influences the development of the instability. The ...
  • Nonlinear development of convective instability within slender flux tubes. II - The effect of radiative heat transport 
    Venkatakrishnan, P (Indian Academy of Sciences, 1985-03)
    Inclusion of radiative heat transport in the energy equation for a slender flux tube leads to oscillations of the tube. The amplitude of the oscillations depends on the radius of the tube when lateral heat exchange alone ...
  • Nonlinear response of slender magnetic flux tubes to external pressure fluctuations 
    Venkatakrishnan, P (Springer, 1986-04)
    The effect of applying external pressure fluctuations on slender flux tubes is studied as a nonlinear initial value problem. It is shown that persistent nonlinear resonant response to pressure fluctuations is possible for ...
  • Nonpotential magnetic fields at sites of gamma-ray flares 
    Hagyard, M. J; Venkatakrishnan, P; Smith, J. B. Jr (American Astronomical Society, 1990-06)
    The relation between the degree of nonpotentiality of photospheric magnetic fields and the occurrence of gama-ray flares is examined to determine whether there are special signatures of the stressed fields for this type ...
  • Observability of Coronal Heating Processes 
    Venkatakrishnan, P (Kluwer Academic Publishers, 1996)
    The mechanisms that could possibly heat the corona are briefly reviewed with emphasis on their observability. Observing enhanced wave flux at footpoints of active regions would confirm wave heating. Observation of nonthermal ...
  • On the absorption of He I 10830 Å line by spicules 
    Venkatakrishnan, P; Jain, S. K (Astronomical Society of India, 1983)
    The possible applications of the time-dependent measurements of the equivalent width of the He I 10830 A line for a better understanding of the growth of spicules and the evolution of coronal holes and x-ray bright points ...
  • On the correlation between line width and line depth of the solar HeI 1083 NM line 
    Venkatakrishnan, P; Sakurai, T; Suematsu, Y; Ichimoto, K (Astronomical Society of India, 1997)
    Seven sets of spectra in the region of the HeI 1083 nm absorption line of the active region NOAA 7558 + 7562 near the west limb, obtained at Norikura Solar Observatory, National Astronomical Observatory, Japan have been ...
  • On the evaluation of magnetic shear from H-alpha pictures 
    Venkatakrishnan, P (Kluwer Academic Publishers, 1993-01-10)
    It is shown that pre-flare activity in H-alpha filaments is unrelated to changes in magnetic shear. Changes in the shear angle are found to be related to either redeployment of the sources of magnetic flux relative to the ...

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