IIA Institutional Repository

Browsing by Author "Singh, J"

Browsing by Author "Singh, J"

Sort by: Order: Results:

  • Omnipresent long-period intensity oscillations in open coronal structures 
    Krishna Prasad, S; Banerjee, D; Van Doorsselaere, T; Singh, J (EDP Sciences, 2012-10)
    Context. Quasi-periodic propagating disturbances in coronal structures have been interpreted as slow magneto-acoustic waves and/or periodic upflows. It is important to understand the nature of these disturbances before ...
  • On the Application of the Equal-contrast Technique to Ca-K Data from Kodaikanal and Other Observatories 
    Singh, J; Priyal, Muthu; Ravindra, B; Bertello, Luca; Pevtsov, Alexei A (American Astronomical Society, 2022-03-10)
    The "equal-contrast technique" (ECT) methodology, developed by Singh et al. to generate uniform long time series of Ca-K images obtained during the 20th century from the Kodaikanal Observatory (KO), improved the correlation ...
  • On the disappearance of H-alpha filaments and soft X-ray enhancements as seen from Yohkoh SXT 
    Singh, J; Sakurai, T; Ichimoto, K (Astronomical Society of India, 2001)
    We have studied H-alpha images of the sun taken at Kodaikanal and Mitaka observatories and soft X-ray images obtained by SXT onboard Yohkoh for the years 1993 and 94. From events of disappearing quiescent H-alpha filaments ...
  • On the eruption of prominences and disappearance of quiescent filaments 
    Singh, J; Gupta, S. S (Springer, 1995-05)
    We suggest the following heuristic model for the evolution of a quiescent filament. The middle part of the filament rises due to heating, while its ends remain anchored in the chromosphere; and a kink appears in the H alpha ...
  • On the formation of a helmet streamer on January 24, 1992 at the south-west limb 
    Singh, J; Sakurai, T; Ichimoto, K; Hiei, E (Astronomical Society of India, 2000)
    We have analysed the soft X-ray images of the sun obtained with the YOHKOH satellite, white light coronal images observed at Mauna Loa and H-alpha pictures of the sun taken at Mitaka and Kodaikanal to study helmet streamers. ...
  • On the Fractal Structure of Solar Supergranulation 
    Paniveni, U; Krishan, V; Singh, J; Srikanth, R (Springer, 2005-10)
    We employ fractal analysis to study the complexity of supergranulation structure using the Solar and Heliospheric Observatory (SOHO) dopplergrams. Our data consists of 200 visually selected supergranular cells, for which ...
  • On the performance of a dual-beam polarimeter at Kodaikanal tower telescope 
    Nagaraju, K; Sankarasubramanian, K; Rangarajan, K. E; Ramesh, K. B; Singh, J; Devendran, P; Hariharan (Astronomical Society of India, 2008-09)
    Calibration and characterization of a dual-beam polarimeter installed at Kodaikanal Tower Telescope (KTT) for spectropolarimetric observations are presented in this paper. It was found that a slit width of 48 μ is optimum ...
  • Optical design of visible emission line coronagraph on Indian space solar mission Aditya-L1 
    Raj Kumar, Nalla; Prasad, B. R; Singh, J; Venkata Suresh, Narra (Springer, 2018-04)
    The ground based observations of the coronal emission lines using a coronagraph are affected by the short duration of clear sky and varying sky transparency. These conditions do not permit to study small amplitude variations ...
  • Optical observational programs at the Indian Institute of Astrophysics 
    Singh, J; Ravindra, B (Astronomical Society of India, 2011)
    The Indian Institute of Astrophysics has been making optical observations of the sun for more than a century by taking images of the sun in continuum to study the photosphere, Ca-K line and H-alpha line in order to study ...
  • Oscillations in active region fan loops: observations from EIS/Hinode and AIA/SDO 
    Krishna Prasad, S; Banerjee, D; Singh, J (Springer, 2012-11)
    Active region fan loops in AR 11076 were studied, in search of oscillations, using high cadence spectroscopic observations from Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode combined with imaging sequences ...
  • Periodic and Quasi-Periodic Variations in the Ca K Index During the 20th Century Using Kodaikanal Data 
    Priyal, Muthu; Singh, J; Ravindra, B; Chandar Shekar, B (Springer, 2019-09)
    We have digitized the Ca K images obtained at Kodaikanal Observatory with a pixel resolution of 0.86 arcsec and 16-bit readout to achieve better spatial and photometric accuracy. In addition to the general photometric ...
  • Photography of Solar Corona Using Indian Air Force Aeroplane 
    Ramani, M; Cowsik, R; Singh, J; Shukla, A. K (Wg. Cdr.); Ravi Shekar (Sqn. Ldr.); Narayana, P. V. S (Fg. Offr); Shaji, P. K (Fg. Offr.); Paul, S. K (Fg. Offr.); Shelkey, S. N (J.W.O); Babu, K. R (J.W.O); Kamble, V. B (Indian Institute of Astrophysics, Bangalore, 1997)
    The teams of the Indian Air Force participated actively in the programme. They made several supersonic flights to follow shadow zone of the moon on earth along the path of totality, thereby extending thte duration of ...
  • The Physical Conditions in a Polar Coronal Hole and Nearby Regions from Norikura and SOHO Observations 
    Raju, K. P; Sakurai, T; Ichimoto, K; Singh, J (The American Astronomical Society, 2000-11)
    The distribution of emission-line intensities, Doppler velocities, and line widths in a polar coronal hole and nearby regions are obtained from the spectroscopic observations carried out on 1998 November 3 at the Norikura ...
  • Polar Network Index as a Magnetic Proxy for the Solar Cycle Studies 
    Priyal, M; Banerjee, D; Karak, B. B; Munoz-Jaramillo, A; Ravindra, B; Choudhuri, A. R; Singh, J (IOP Publishing, 2014-09-20)
    The Sun has a polar magnetic field which oscillates with the 11 yr sunspot cycle. This polar magnetic field is an important component of the dynamo process which operates in the solar convection zone and produces the sunspot ...
  • Possible Evidence of Long-Term Oscillations in the Solar Atmosphere 
    Raju, K. P; Singh, J; Srikanth, R; Chou, Dean-Yi; CA, TON team (Springer, 2001-03)
    We have obtained the temporal correlation function, Q(t), from time sequences of Caii K filtergrams and Dopplergrams from Antarctica, Taiwan Oscillation Network (TON) and Solar and Heliospheric Observatory (SOHO). Q(t) ...
  • Proposed National Large Solar Telescope 
    Singh, J (Indian Academy of Sciences, 2008-06)
    Sun’s atmosphere is an ideal place to study and test many magnetohydrodynamic (MHD) processes controlling turbulent plasma. We wish to resolve some of the finest solar features (which remain unresolved presently) and study ...
  • 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 ...
  • Relationship between horizontal flow velocity and cell lifetime for supergranulation from SOHO Dopplergrams 
    Paniveni, U; Krishan, V; Singh, J; Srikanth, R (Royal Astronomical Society, 2004-02-01)
    A study of 50 supergranular cells obtained from Solar and Heliospheric Observatory (SOHO) Dopplergrams was undertaken in order to investigate the relationship between the lifetime (T) and the horizontal flow velocity (vh) ...
  • Relationship between horizontal flow velocity and cell size for supergranulation using SOHO Dopplergrams 
    Krishan, V; Paniveni, U; Singh, J; Srikanth, R (Royal Astronomical Society, 2002-07)
    A study of 90 supergranular cells obtained from SOHO Dopplergrams was undertaken in order to investigate a possible relation between the sizes and peak horizontal velocities of the cells. For the sample obtained, the two ...
  • Results of 1995 eclipse observation and observing program for 1998 and 1999 eclipses 
    Singh, J (Astronomical Society of India, 1998)
    We, at the Institute of Astrophysics, conducted ten experiments from two places namely Neem Ka Thana in Rajasthan and Kalpi in Uttar Pradesh. The experiments involved high spatial and spectral resolution spectroscopy to ...

Search DSpace

Browse

My Account