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Browsing by Author "Ichimoto, K"

Browsing by Author "Ichimoto, K"

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  • Detection of cooler loop-tops in a coronal structure 
    Singh, J; Sakurai, T; Ichimoto, K (Anita Publications, 2004-12)
    We have obtained off the limb' spectroscopic observations covering a coronal region of 200" x 500" in [Fe x] 6374 A and [Fe xi) 7892 A emission lines simultaneously. Yohkoh soft X-ray images of the sun showed two independent ...
  • 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. ...
  • 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 ...
  • 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 ...
  • 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 ...
  • 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 ...
  • On the correlation between line width and line depth of the solar HeI 1083 NM line 
    Venkatakrishnan, P; Sakurai, T; Suematsu, Y; Ichimoto, K (Astronomical Society of India, 1997)
    Seven sets of spectra in the region of the HeI 1083 nm absorption line of the active region NOAA 7558 + 7562 near the west limb, obtained at Norikura Solar Observatory, National Astronomical Observatory, Japan have been ...
  • 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 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. ...
  • 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 ...
  • Spectroscopic Observation of Coronal Waves 
    Sakurai, T; Ichimoto, K; Raju, K. P; Singh, J (Springer, 2002-10)
    A time sequence over 80 min of coronal green-line spectra was obtained with a corona- graph at the Norikura Solar Observatory. Doppler velocities, line intensities, and line widths were derived through fitting a single ...
  • Spectroscopic Studies of Solar Corona VI: Trend in Line-width Variation of Coronal Emission Lines with Height Independent of the Structure of Coronal Loops 
    Singh, J; Sakurai, T; Ichimoto, K; Muneer, S (Indian Academy of Sciences, 2006-09)
    We have obtained spectroscopic observations in coronal emission lines by choosing two lines simultaneously, one [Fe x] 6374Å and the other [Fe xi] 7892Å or [Fe xiii] 10747Å or [Fe xiv] 5303 Å. We found that in 95 per cent ...
  • Spectroscopic Studies of Solar Corona VIII. Temperature and Non-Thermal Variations in Steady Coronal Structures 
    Singh, J; Sakurai, T; Ichimoto, K; Muneer, S; Raveendran, A. V (Springer, 2006-07)
    With a view to investigate variations in parameters of coronal emission lines over a large range of radial distance from the limb, raster scans were made with sufficiently long exposure times on several days during September ...
  • Spectroscopic Studies of the Solar Corona - V. Physical Properties of Coronal Structures 
    Singh, J; Sakurai, T; Ichimoto, K; Muneer, S (Springer, 2003-02)
    Spectra around the 6374 Å [Fex] and 7892 Å [Fexi] emission lines were obtained simultaneously with the 25-cm coronagraph at Norikura Observatory covering an area of 200' '×500' ' of the solar corona. The line width, peak ...
  • Spectroscopic Studies of the Solar Corona III. Density Diagnostics Using the Infrared Lines of Fe XIII 
    Singh, J; Sakurai, Takashi; Ichimoto, K; Takeda, Aki (Astronomical Society of Japan, 2002)
    We have obtained spectrographic observations of several coronal regions in three emission lines (6374Å [Fe X ], 10747Å [Fe XIII ], and 10798Å [Fe XIII ]) simultaneously. The 25-cm coronagraph at Norikura Observatory and ...
  • Spectroscopic Studies of the Solar Corona. IV. Physical Properties of Coronal Structure 
    Singh, J; Ichimoto, K; Sakurai, T; Muneer, S (The American Astronomical Society, 2003-03)
    We obtained spectrographic observations of several coronal structures at the limb overlying the sunspot regions, simultaneously in the Fe XIV (5303 Å) and Fe X (6374 Å) emission lines on several days, and simultaneously ...
  • A Spectroscopic Study of the Solar Corona from Norikura and SOHO data 
    Raju, K. P; Sakurai, T; Ichimoto, K (International Astronomical Union, 2001)
    We report the results from a spectroscopic study of the solar corona, wherein, we examine some of the current problems in the corona, such as the plume-interplume differences in coronal holes, coronal loops in active regions ...
  • Thermal structure of coronal loops as seen with Norikura coronagraph 
    Krishna Prasad, S; Singh, J; Ichimoto, K (IOP Publishing, 2013-03-10)
    The thermal structure of a coronal loop, both along and across the loop, is vital in determining the exact plasma heating mechanism. High-resolution spectroscopic observations of the off-limb corona were made using the ...

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