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Browsing by Author "Venkatakrishnan, P"

Browsing by Author "Venkatakrishnan, P"

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  • High resolution imaging of the sun and other extended sources 
    Krishnakumar, V; Venkatakrishnan, P (Astronomical Society of the Pacific, 1998)
    The functional form of the long exposure OTF P(u,v) is known (Fried 1966; Kirshnakumar & Venkatakrishnan 1997a) and i(x,y) is what we record. The knowledge of P(u,v) is complete once ro is estimated. Our aim is to recover ...
  • Imaging with insolated mirrors 
    Venkatakrishnan, P; Sridharan, R; Gupta, S. K (Astronomical Society of India, 2005-09)
    Modern solar telescope designs are different from the conven- tional concept of vacuum telescopes. These new designs are "open" telescopes which try to minimize the temperature difference between various parts of the ...
  • Implications of Tension-Free Equilibria for Pre-Flare Energy Build UP 
    Venkatakrishnan, P (International Astronomical Union, 1990)
    The downward tension force is known to be the extremely small at the locations of highly sheared magnetic fields. The free energy in such tension free fields is shown to be dependent on the plasma density. The excess of ...
  • Influence of solar wind variability of the recurrence of droughts 
    Venkatakrishnan, P (D. Reidel Publishing Co, 1982-11)
    The observed effects of solar flares and interplanetary sector crossings seem to indicate that particle precipitation in the earth's upper atmosphere decreases cyclonic activity in the troposphere. As an extrapolation to ...
  • Inhibition of convective collapse of solar magnetic flux tubes by radiative diffusion 
    Venkatakrishnan, P (Nature Publishing Group, 1986-07)
    Proctor and Weiss (1982) have indicated that the interaction of convection with a magnetic field leads to an intermittent distribution of magnetic flux. Such a process can lead to 'equipartition fields' of 700 G which ...
  • Intensity Changes in Sunspots and Starspots 
    Venkatakrishnan, P (Astronomical Society of India, 1978-12)
  • Issues with external occultation of a coronagraph 
    Bayanna, A. R; Mathew, S. K; Sankarasubramanian, K; Venkatakrishnan, P; Singh, J; Prasad, B. R (Springer, 2011-04)
    This paper addresses some of the issues related to externally occulted solar coronagraph; vignetting and achievable resolution due to an external occulter. The analytical expression by Evans (J Opt Soc Am 38:1083–1085, ...
  • 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 ...

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