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Browsing by Author "Venkatakrishnan, P"

Browsing by Author "Venkatakrishnan, P"

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  • Ellipsometry of Coelostat Coatings Using a Babinet Compensator: Simulation of the Experimental Accuracy 
    Sankarasubramanian, K; Venkatakrishnan, P (Kluwer Academic Publishers, 1996-08)
    The precise measurement of solar magnetic fields requires an accurate measurement of the Muller matrix of the optical components in the path of the light beam, which again requires a careful measurement of the optical ...
  • Enhanced He{I} Absorption at the Feet of Solar X-Ray Loops 
    Venkatakrishnan, P; Sakurai, T; Suematsu, Y; Ichimoto, K (Astronomical Society of Japan, 1996)
    A comparison of He{I} spectroheliograms and Yohkoh soft X-ray images of active regions indicates that He{I} absorption is enhanced at the feet of hot X-ray loops. It is suggested that the conduction of heat from the loops ...
  • Estimation of Fried's Parameter From Specklegrams of Solar Features 
    Sridharan, R; Venkatakrishnan, P; Verma, V. K (Springer, 2002-12)
    A few methods of estimating Fried's parameter (r 0) from specklegrams of solar features are described. Some of these methods were used to estimate r 0 for the speckle data obtained from Kodaikanal Observatory (KO), Uttar ...
  • Evolution of Currents of Opposite Signs in the Flare-productive Solar Active Region NOAA 10930 
    Ravindra, B; Venkatakrishnan, P; Tiwari, S. K; Bhattacharyya, R (IOP Publishing, 2011-10-10)
    Analysis of a time series of high spatial resolution vector magnetograms of the active region NOAA 10930 available from the Solar Optical Telescope SpectroPolarimeter on board Hinode revealed that there is a mixture of ...
  • Evolution of magnetic field twist and tilt in active region NOAA 10930 
    Ravindra, B; Venkatakrishnan, P; Tiwari, S. K (World Scientific Publishing Company, 2010)
    Magnetic twist of the active region has been measured over a decade using photospheric vector field data, chromospheric Hα data, and coronal loop data. The twist and tilt of the active regions have been measured at the ...
  • The evolution of the Net Twist Current and the Net Shear Current in active region NOAA 10930 
    Suthar, Y; Venkatakrishnan, P; Ravindra, B; Jaaffrey, S. N. A (Springer, 2014-07)
    The electric current exists because of the non-potential magnetic field in solar active regions. We present the evolution of net current in the solar active region NOAA 10930 as the sum of shear current and twist current ...
  • The evolutton of the magnetic structure of the solar corona with the solar cycle 
    Dikpati, M; Choudhuri, A. R; Venkatakrishnan, P (Astronomical Society of the Pacific, 1996)
  • Fizeau mask interferometry of solar features using the multi-application solar telescope at the udaipur solar observatory 
    Bayanna, A. R; Venkatakrishnan, P; Rengaswamy, S; Mathew, S. K. (Springer, 2020-02)
    Efforts are made to demonstrate high-resolution observations of the solar atmosphere using spatial interferometry. Covering the telescope pupil with a Fizeau mask consisting of two small circular apertures separated by a ...
  • Flow of Gas along a Magnetic field with Time-Dependent Geometry 
    Hasan, S. S; Venkatakrishnan, P (Indian Institute of Astrophysics, Bangalore, 1980)
    The flow of gas along a magnetic field with time dependent geometry has been studied. It is seen that the velocity of the flow in the direction of the magnetic field depends both on the magnitude of the velocity of flow ...
  • Flux emergence in the solar active region NOAA 11158: the evolution of net current 
    Vemareddy, P; Venkatakrishnan, P; Karthikreddy, S (IOP Publishing, 2015-09)
    We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region (AR) NOAA 11158 obtained from the Helioseismic and Magnetic Imager. We ...
  • Frequency response of magnetic flux sheaths 
    Venkatakrishnan, P (D. Reidel Publishing Co., 1979-08)
    When a sound wave is incident on a magnetic flux sheath, it causes fluctuations in the mean magnetic field of the sheath. We have calculated the space-average of the longitudinal component of these fluctuations and plotted ...
  • 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 ...

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