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Browsing by Author "Singh, J"

Browsing by Author "Singh, J"

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  • 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 ...
  • Detection of Short-Period Coronal Oscillations during the Total Solar Eclipse of 24 October, 1995 
    Singh, J; Cowsik, R; Raveendran, A. V; Bagare, S. P; Saxena, A. K; Sundararaman, K; Krishan, V; Naidu, N; Samson, J. P. A; Gabriel, F (Springer, 1997-02)
    An experiment to search for short-period oscillations in the solar corona was conducted during the total solar eclipse of 1995 October 24 at Kalpi, India. The intensity in the continuum, centred around 5500 Å and with a ...
  • Determination of the choromospheric quiet network element area index and its variation during 2008 and 2011 
    Singh, J; Ravindra, B; Selvendran, R; Kumaravel, P; Priyal, M; Priya, T. G; Amareswari, K (Chinese Academy of Sciences, 2012-02)
    Generally it has been considered that the plages and sunspots are the main contributors to the solar irradiance. There are small scale structures on the sun with intermediate magnetic fields that could also contribute ...
  • Determining the variations of Ca–K index and features using century-long equal-contrast images from Kodaikanal observatory 
    Singh, J; Priyal, M; Ravindra, B (IOP Publishing, 2021-02-20)
    In an earlier analysis of Ca–K spectroheliograms obtained at the Kodaikanal Observatory, the "Good" images were used to investigate variations in the chromosphere. However, the contrast of the images varied on a day-to-day ...
  • Differences in heliographic positions and rotation velocities of sunspot groups from various observatories 
    Poljancic, I; Brajsa, R; Hrzina, D; Wohl, H; Hanslmeier, A; Potzi, W; Baranyi, T; Ozguc, A; Singh, J; Ruzdjak, V (Hvar Observatory, 2011)
    Measured positions of sunspot groups that differ in format, precision and observing procedure are collected from various data sets: GPR (Greenwich Photoheliographic Results), SOON/USAF/NOAA (Solar Optical Observing ...
  • Digitization of Kodaikanal Data 
    Singh, J; Muneer, S; Bagare, S. P; Rangarajan, K. E; Ramesh, K. B; Varghese, B. A; Samson, J. P. A; Devendran, P; Hariharan, G (Astronomical Society of India, 2003)
    In this report we describe a digitizer developed in the laboratories of the Indian Institutes of Astrophysics (IIA) to digitize the large amount of solar synoptic data obtained since 1904 at Kodaikanal. We show a sample ...
  • Distribution of Supergranular Sizes 
    Srikanth, R; Singh, J; Raju, K. P (The American Astronomical Society, 2000-05)
    A gradient-based method of tessellation was applied to SOHO Dopplergrams and to Ca II K filtergrams in order to study the cellular pattern of the solar surface, in specific the geometric relationship between the tessellation ...
  • The Distribution of the Quiet Sun Photospheric Magnetic Flux 
    Srikanth, R; Singh, J; Bagare, S. P (Astronomical Society of India, 2002-12)
    A gradient-based tessellating algorithm is used to study the magnetic field structure of the quiet Sun photosphere using SoRO full disk magnetograms. We find that the field is not uniformly distributed, but parcelled ...
  • Do the Line Widths of Coronal Emission Lines Increase with Height above the Limb? 
    Singh, J; Sakurai, T; Ichimoto, K (University of Chicago Press, 2006-03)
    In our earlier studies we obtained off-the-limb spectroscopic observations in a number of forbidden emission lines ([Fe X–XIV]) to study the physical properties and their temporal variations in steady coronal structures. ...
  • Eclipse observations of coronal emission lines. I.[FeX]6374 A profiles at the eclipse of 16 February 1980 
    Singh, J; Bappu, M. K. V; Saxena, A. K (Indian Academy of Sciences, 1982-09)
    Coronal spectra during the total solar eclipse of February 16, 1980, obtained in the 6374 A (forbidden Fe X) line using a multislit spectrograph are discussed. The dispersion of these spectra is 2.5 A/mm. The observed line ...
  • Effects of magnetic shear, spot, and plage rotation on prominence evolution 
    Rausaria, R. R; Gupta, S. S; Selvendran, R; Raman, K. S; Singh, J (Kluwer Academic Publishers, 1993-08)
    We have studied the evolution of two dark H-alpha filaments as prominences during their disk passage from February 12 to February 19, 1992 and from March 6 to March 17, 1992, using Kodaikanal Observatory H-alpha and Ca II ...
  • Emission lines of inner corona observed during the total solar eclipse of 1980 February 16 
    Singh, J; Rajamohan, R; Raheem, K. C. A (Astronomical Society of India, 1983-12)
    Spectrograms of the inner solar corona were obtained during the 1980 total solar eclipse. Two Ebert-Fastie type spectrographs with circular slits were used to obtain spectra on the east and the west at 1.06 R. These ...
  • Existence of Nanoparticle Dust Grains in the Inner Solar Corona? 
    Singh, J; Sakurai, T; Ichimoto, K; Hagino, M; Yamamoto, T. T (The American Astronomical Society, 2004-06)
    Motivated by the recent paper by Habbal et al., we have made spectroscopic observations in the wavelength range of 1072.8-1079.0 nm of the solar corona above the coronal hole region on several days using a coronagraph. We ...
  • Exploring the outer emission corona spectroscopically by using Visible Emission Line Coronagraph (VELC) on board ADITYA-L1 mission 
    Singh, J; Prasad, B. R; Venkata Suresh, Narra; Amit Kumar (Elsevier B.V, 2019-07-17)
    It is very important to make the spectrographic observations of the outer emission corona in number of emission lines simultaneously in view of the results of the observations made in [Fe x] 6374 A, [Fe xi] 7892 A, [Fe ...
  • Extinction measurements at Leh 
    Singh, J; Bhattacharyya, J. C; Raveendran, A. V; Mohin, S; Ashoka, B. N (Astronomical Society of India, 1988-03)
    Observations were started at Leh in 1984 with a view to finding the possibility of setting up an astronomical observatory for infrared observations. Results of extinction measurements in UBV bands obtained on 12 nights ...
  • Fabry-Perot Interferometric Observations of the Solar Corona in the Green Line 
    Raju, K. P; Singh, J; Muralishankar, S (Indian Institute of Astrophysics, Bangalore, 1997)
    An imaging Fabry-Perot interferometer was designed and used for coronal observations in the green line (FeXIV) 5303 Armstrong. The observations were carried our at Nim Ka Thana, Rajasthan, India during the total solar ...
  • Fe XIV green/Fe XIII infrared line ratio diagnostics 
    Srivastava, A. K; Singh, J; Dwivedi, B. N; Muneer, S; Sakurai, T; Ichimoto, K (Astronomical Society of India, 2007-12)
    We consider the first 27-level atomic model of Fe XIII (5.9 K < log Te < 6.4 K) to estimate its ground level populations, taking account of electron as well as proton collisional excitations and de-excitations, radiative ...
  • Fractal structure of solar supergranulation 
    Paniveni, U; Krishan, V; Singh, J; Srikanth, R (European Space Agency, 2005-12)
    We employ fractal analysis to study the complexity of supergranulation structure using the solar and Heliospheric Observatory (SOHO) dopplergrams. Our data consist of 200 visually selected Supergranular cells, for which ...
  • Full-disk synoptic observations of the chromosphere using Hα telescope at the Kodaikanal Observatory 
    Ravindra, B; Prabhu, K; Rangarajan, K. E; Bagare, S. P; Singh, J; Kemkar, P. M. M; Thulasidharen, K. C; Gabriel, F; Selvendran, R (IOP Publishing, 2016-08)
    This paper reports on the installation and observations of a new solar telescope installed on 2014 October 7 at the Kodaikanal Observatory. The telescope is a refractive type equipped with a tunable Lyot Hα filter. A CCD ...
  • H-alpha flare of 14 March, 1984 -- Evidence for reconnection? 
    Sundararaman, K; Aleem, S. M; Singh, J; Selvendran, R; Thiagarajan, R (Springer, 1994-01)
    Kodaikanal H-alpha monochromatic and white-light observations are used to study the circular flare of 14 March, 1984. We report here the dynamic activity of the H-alpha filament, which attained a severe twist before erupting ...

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