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Browsing by Author "Singh, J"

Browsing by Author "Singh, J"

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  • Lifetimes and sizes of supergranular cells 
    Raju, K. P; Srikanth, R; Singh, J (Astronomical Society of India, 1999)
    Supergranulation is the surface manifestation of large scale solar convection. Since there is a strong correspondence between supergranulation pattern and Ca K chromospheric network, lifetimes and sizes may be obtained ...
  • Long Term Variations in Chromospheric Features from Ca-K Images at Kodaikanal 
    Priyal, M; Singh, J; Ravindra, B; Priya, T. G; Amareswari, K (Springer, 2014-01)
    There is a collection of about 100 years of Ca-K line spectroheliograms at the Kodaikanal Observatory (KKL) obtained on daily basis with a single instrument that can be used to study long term variations of various ...
  • Long-term variations in the intensity of plages and networks as observed in Kodaikanal Ca-K digitized data 
    Priyal, M; Singh, J; Ravindra, B; Kameshwaran Rathina, Somasundaram (Springer, 2017-07)
    In our previous article (Priyal et al. in Solar Phys. 289, 127, 2014) we have discussed the details of observations and methodology adopted to analyze the Ca-K spectroheliograms obtained at the Kodaikanal Observatory (KO) ...
  • Magnetic nature of coronal loops 
    Singh, J; Muneer, S; Sakurai, T; Ichimoto, K (Astronomical Society of India, 2007-12)
    It is generally believed that the magnetic pressure is much higher than the gas pressure in the coronal loops and these loops are isothermal in nature. We made systematic observations of four strong coronal emission lines ...
  • Mid-term quasi-periodicities in the CaII-K plage index of the Sun and their implications 
    Chowdhury, P; Gokhale, M. H; Singh, J; Moon, Y.-J (Springer, 2016-02)
    We present results of the fast Fourier transform (FFT), the MEM analysis, and the wavelet analysis (WA), of the temporal variation of the monthly disk integrated “CaII-K plage-area and enhanced network (EN) area” hereafter ...
  • Modeling a Coronal Mass Ejection as a Magnetized Structure with EUHFORIA 
    Sindhuja, G; Singh, J; Asvestari, E; Prasad, B. R (IOP Publishing, 2022-01-20)
    We studied an Earth-directed coronal mass ejection (CME) that erupted on 2015 March 15. Our aim was to model the CME flux rope as a magnetized structure using the European Heliospheric Forecasting Information Asset (EUHFORIA). ...
  • Multislit spectrophotometry of the corona 
    Saxena, A. K; Singh, J; Gabriel, F (Indian National Science Academy, 1981)
  • 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 ...
  • Nature of Tilt Angles of Sunspot Groups During the 22nd Solar Cycle 
    Muneer, S; Singh, J (Springer, 2002-10)
    Daily white-light images from Kodaikanal Observatory have been utilized to study the nature of tilt angles of sunspot groups during the 22nd solar cycle. 2416 spot groups have been measured to find the tilt angle. An average ...
  • Network and plage indices from Kodaikanal Ca-K data 
    Raju, K. P; Singh, J (IOP Publishing, 2014-02)
    The Ca II K filtergrams from Kodaikanal Solar Observatory have been used to study solar activity. The images are dominated by the chromospheric network and plages. Programs have been developed to obtain the network and ...
  • A new method of calibration of photographic plates from three historic data sets 
    Tlatov, A. G; Pevtsov, A. A; Singh, J (Springer, 2009-04)
    We analyze the synoptic data taken in the Ca ii K spectral line with spectroheliographs at Kodaikanal Observatory from 1907 to 1999, at Mount Wilson Observatory from 1915 to 1985, and at the National Solar Observatory at ...
  • A new technique to study the variability of the Sun 
    Singh, J (Indian Institute of Astrophysics, Bangalore, 1988)
    A method has been developed to take the high resolution spectra in ionized calcium K line at different latitudes and integrated over visible 180/sup0/ longitude. These spectra have been analysed to study the variability ...
  • Observation of Intensity Oscillations in Corona during the Total Solar Eclipse of October 24, 1995 
    Singh, J (Indian Institute of Astrophysics, Bangalore, 1997)
    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 Armsrong and ...
  • Observations of the Corona at the Eclipse of 1983 June 11. I. Temperature and Rotation of the Corona from 5303A and 6374A profiles 
    Singh, J; Sivaraman, K. R; Rajamohan, R (Indian Institute of Astrophysics, Bangalore, 1988)
    During the total solar eclipse of 1983 June 11, coronal spectra were obtained in the 5303A (Fe XIV) line using the multislit spectrograph at a dispersion of 2.17A mm-1 . The line profiles measured at 113 locations from ...
  • Observing conditions for optical astronomy at Leh 
    Singh, J; Bhattacharyya, J. C; Babu, G. S. D; Ashoka, B. N; Appakutty, M; Rangarajan, K. E; Kutty, K. N; Moorthy, V; Selvakumar, G; Michael, P; Muniyandi, A; Gabriel, F (Astronomical Society of India, 1989-09)
    The sky and atmospheric conditions at Leh have been monitored since 1984 with a view to determining its suitability as a site for a high-altitude observatory. During May-November, 1987, relative humidity and other parameters ...
  • 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. ...

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