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Browsing by Author "Venkatakrishnan, P"

Browsing by Author "Venkatakrishnan, P"

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  • On the flare induced high-frequency global waves in the sun 
    Kumar, B; Mathur, S; García, R. A; Venkatakrishnan, P (Institute of Physics, 2010-03-01)
    Recently, Karoff & Kjeldsen presented evidence of strong correlation between the energy in the high-frequency part (5.3 < ν < 8.3 mHz) of the acoustic spectrum of the Sun and the solar X-ray flux. They have used disk-integrated ...
  • On the line profile changes observed during the X2.2 class flare in the active region NOAA 11158 
    Bayanna, A. R; Kumar, B; Venkatakrishnan, P; Mathew, S. K; Ravindra, B; Mathur, S; Garcia, R. A (IOP Publishing, 2014-02)
    The solar active region NOAA 11158 produced a series of flares during its passage through the solar disk. The first major flare (of class X2.2) of the current solar cycle occurred in this active region on 2011 February 15 ...
  • 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 ...
  • On the saturation of the refractive index structure function. I - Enhanced hopes for long baseline optical interferometry 
    Venkatakrishnan, P; Chatterjee, S (Royal Astronomical Society, 1987-01)
    The Kolomogorov- Obukhov law for the refractive index structure function is shown to be only an approximation valid in the inertial sub range of turbulence. The inclusion of saturation effects for larger separations leads ...
  • On the saturation of the refractive index structure function. II - Influence of the correlation length on astronomical 'seeing' 
    Venkatakrishnan, P (Royal Astronomical Society, 1987-12)
    A physical length scale in the wavefront corresponding to the parameter (r/sub0/) characterizing the loss in detail in a long exposure image is identified, and the influence of the correlation scale of turbulence as r/sub ...
  • Onset of Hydrodynamic Non-Equilibrium in Helmet Streamers 
    Venkatakrishnan, P (Kluwer Academic Publishers, 1996-06)
    The steady-state solar wind solution is examined for different geometries of the flow tube that mimics a helmet streamer. Onset of non-equilibrium is seen whenever the spatial variation of the flow geometry crosses critical ...
  • Optical astronomyusing radio techniques:Imaging capella with unprecedented resolution 
    Venkatakrishnan, P (Indian Academy of Sciences, 1996-08)
  • Performance Evaluation of Adaptive Optics Systems 
    Sridharan, R; Raja Bayanna, A; Srivastava, N; Kumar, B; Ravindra, B; Gupta, S. K; Jain, N; Ambastha, A; Venkatakrishnan, P (Astronomical Society of India, 2003)
    Adaptive Optics (AO) systems improve the resolution of ground based telescopes and allow for long exposure images. Their performance depends on the seeing conditions at the time of observations. In this paper, we evaluate ...
  • A personal-computer-based imaging Stokes polarimeter for solar observations 
    Ananth, A. V; Venkatakrishnan, P; Narayanan, R. S; Bhattacharyya, J. C (Springer, 1994-05)
    For measurements of vector magnetic field over solar active regions, a Stokes polarimeter for studying the polarization profiles on selected spectral lines is described. This paper gives details of the relevant charged ...
  • A phenomenological, kinematical model of the coronal magnetic fields in terms of thin flux tubes rising from the photosphere 
    Gokhale, M. H; Venkatakrishnan, P (Indian Academy of Sciences, 1978-11)
    A kinematical model is necessary for understanding the gross structure of the coronal magnetic field and its slow evolution in consistency with the small scale structure of the photospheric fields. Here we have developed ...
  • Proposed visible emission line space solar coronagraph 
    Singh, J; Prasad, B. R; Venkatakrishnan, P; Sankarasubramanian, K; Banerjee, D; Bayanna, R; Mathew, S; Murthy, J; Subramaniam, P; Ramesh, R; Kathiravan, S; Nagabhushana, S; Mahesh, P. K; Manoharan, P. K; Uddin, W; Sriram, S; Amit Kumar; Srivastava, N; Koteswara Rao; Nagendra, C. L; Chakraborty, P; Sriram, K. V; Venkateswaran, R; Krishnamurthy, T; Sreekumar, P; Sarma, K. S; Murthy, R; Navalgund, K. H; Samudraiah, D. R. M; Narayan Babu, P; Patra, A (Indian Academy of Sciences, 2011-01-25)
    The outer atmosphere of the sun – called the corona – has been observed during total solar eclipse for short periods (typically < 6 min), from as early as the eighteenth century. In the recent past, space-based instruments ...
  • Reconstruction of Solar Features from an Image of Partially Eclipsed Sun 
    Krishnakumar, V; Venkatakrishnan, P (Indian Institute of Astrophysics, Bangalore, 1997)
    The photoheliograms obtained at Kodaikanal during the partial eclipse of the Sun on October 24, 1995 were digitised on a PDS microdensitometer. The lunar limb was used as a standard source for the digital reconstruction ...
  • Rotation in close binaries 
    Rajamohan, R; Venkatakrishnan, P (International Astronomical Union, 1980)
  • Science from "Solar X-ray Spectrometer (SOXS)" - Proposed payload onboard Indian satellite 
    Jain, R; Rao, A. R; Deshpande, M. R; Dwivedi, B. N; Manoharan, P. K; Seetha, S; Vahia, M. N; Vats, H. O; Venkatakrishnan, P (Astronomical Society of India, 2000)
    It is proposed to fly a high spectral and temporal resolution "Solar X-ray Spectrometer (SOXS)" onboard Indian satellite to understand the mechanisms of energy release and particle acceleration in solar flares. The SOXS ...
  • A Search for Vector Magnetic Field Variations Associated with the M-Class Flares of 10 June 1991 IN AR6659 
    Hagyard, M. J; Stark, B. A; Venkatakrishnan, P (Kluwer Academic Publishers, 1999-01)
    A careful analysis of a 6-hour time sequence of vector magnetograms of AR6659, observed on 10 June 1991 with the MSFC vector magnetograph, has revealed only minor changes in the vector magnetic field azimuths in the vicinity ...
  • Solar physics at Indian Institute of Astrophysics 
    Venkatakrishnan, P; Krishan, V (Indian Institute of Astrophysics, 1989-12)
  • Spatio-temporal fluctuations in He I 10830 A line parameters - Evidence for spicule formation 
    Venkatakrishnan, P; Jain, S. K; Singh, J; Recely, F; Livingston, W. C (Springer Netherlands, 1992-03)
    The equivalent width, line depth, line width, and Doppler shift of the He i 10830 Å line were extracted from two time series of spectra. Scatter plots of time-averaged line depth, line width, and Doppler shifts, as well ...
  • A Speckle Experiment during the Partial Eclipse 
    Saha, S. K; Nagabhushana, B. S; Ananth, A. V; Venkatakrishnan, P (Indian Institute of Astrophysics, Bangalore, 1997)
    An experiment for the speckle reconstruction of solar features was developed for observing the partial eclipse of the sun as viewed from Bangalore on October 24, 1995. No data could be obtained because of cloudy sky but ...
  • Speckle interferometry at IIA and elsewhere: An overview 
    Venkatakrishnan, P; Saha, S. K; Shevgaonkar, R. K (Tata Institute of Fundamental Reserach, 1988)
    The technique of speckle interferometry, used for compensating the blurring effects of the earth's atmosphere, is briefly outlined. The achievements of this technique by different groups in the world are listed. We then ...

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