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Browsing by Author "Nagaraju, K"

Browsing by Author "Nagaraju, K"

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  • Data processing of visible emission line coronagraph onboard ADITYA-L1 
    Priyal, M; Singh, J; Prasad, B. R; Sumana, Chavali; Kumar, Varun; Mishra, Shalabh; Venkata, S. N; Sindhuja, G; Sasikumar Raja, K; Amit Kumar; Krishnan, Sanal; Hegde, Bhavana; Utkarsha, D; Natarajan, V; Somasundaram, P. K; Nagabhushana, S; Kamath, P. U; Kathiravan, S; Mani, V. T; Basavaraju, Suresh; Chavan, Rajkumar; Vemareddy, P; Ravindra, B; Rajaguru, S. P; Nagaraju, K; Mishra, Wageesh; Joshi, Jayant; Samanta, T; Chatterjee, Piyali; Kathiravan, C; Ramesh, R (Elsevier B.V, 2024-07-01)
    ADITYA-L1 is India's first dedicated mission to observe the Sun and its atmosphere from a halo orbit around L1 point. Visible emission line coronagraph (VELC) is the primary payload on board Aditya-L1 to observe the Sun’s ...
  • Design concepts of EUV polarimeter 
    Khan, Raveena; Nagaraju, K; Phanindra, DVS (SPIE-The International Society for Optical Engineering, 2023-10)
    The solar corona is a complex and dynamic region primarily controlled by the magnetic fields. Hence the routine measurement of these fields is crucial. Magnetic field information remains embedded in the polarization profiles ...
  • Diagnosing chromospheric magnetic field through simultaneous spectropolarimetry in Hα and Ca II 854.2 nm 
    Nagaraju, K; Sankarasubramanian, K; Rangarajan, K. E (Cambridge University Press, 2020)
    Measurement of magnetic field in this layer is challenging both from point of view of observations and interpretation of the data. We present in this work about spectropolarimetric observations of a pore, simultaneously ...
  • Do Hα Stokes V Profiles Probe the Chromospheric Magnetic Field? An Observational Perspective 
    Mathur, Harsh; Nagaraju, K; Joshi, Jayant; de la Cruz Rodriguez, Jaime (American Astronomical Society, 2023-03-20)
    We investigated the diagnostic potential of the Stokes V profile of the Hα line to probe the chromospheric line-ofsight (LOS) magnetic field (BLOS) by comparing the BLOS inferred from the weak field approximation (WFA) ...
  • An efficient modulation scheme for dual beam polarimetry 
    Nagaraju, K; Ramesh, K. B; Sankarasubramanian, K; Rangarajan, K. E (Astronomical Society of India, 2007-09)
    An eight stage balanced modulation scheme for dual beam polarimetry is presented in this paper. The four Stokes parameters are weighted equally in all the eight stages of modulation resulting in total polarimetric efficiency ...
  • Extreme-ultraviolet Polarimetric Diagnostics of the Solar Corona: The Hanle Effect of Ne VIII 770Å 
    Khan, Raveena; Gibson, Sarah E; Casini, Roberto; Nagaraju, K (American Astronomical Society, 2024-08-10)
    Magnetic fields are the primary driver of the plasma thermodynamics in the upper solar atmosphere, especially in the corona. However, magnetic field measurements in the solar corona are sporadic, thereby limiting us from ...
  • Full Stokes polarimetry using dual-frequency liquid crystals 
    Nagaraju, K; Phanindra, D. V. S; Krishna Prasad, S; Shankar Rao, D. S; Sreekumar, P (SPIE-The International Society for Optical Engineering, 2018-07-06)
    In a dual-frequency liquid crystal (DFLC), when the frequency of the applied voltage is more than a critical value (fc), the dielectric anisotropy of the material changes from positive to negative. This causes the director ...
  • High-resolution, high-sensitivity, ground-based solar spectropolarimetry with a new fast imaging polarimeter: I .Prototype characterization 
    Iglesias, F. A; Feller, A; Nagaraju, K; Solanki, S. K (EDP Sciences, 2016-06)
    Remote sensing of weak and small-scale solar magnetic fields is of utmost relevance when attempting to respond to a number of important open questions in solar physics. This requires the acquisition of spectropolarimetric ...
  • Hα full line spectropolarimetry as diagnostics of chromospheric magnetic field 
    Nagaraju, K; Sankarasubramanian, K; Rangarajan, K. E (Indian Academy of Sciences, 2020-12)
    Analysis of spectropolarimetric observations of two circular sunspots located close to disk centre in Hα (6562.8 Å) and Fe i (6569.22 Å) is presented in this paper. The corresponding active region numbers areNOAA 10940 and ...
  • An Image Auto Guider System for Kodaikanal Tower Tunnel Telescope 
    Mathur, Harsh; Thulasidharen, K. C; Hemanth, P; Nagaraju, K; Rajalingam, M (World Scientific Publishing, 2023-02)
    The Kodaikanal Tower Tunnel Telescope (KTT) is a three-mirror Coelostat-based Solar telescope. An inherent variable image drift is present in the KTT which is detrimental to observations particularly to slit-based spectroscopic ...
  • Magnetic and velocity properties of G-band bright points around a pore 
    Rangarajan, K. E; Sankarasubramanian, K; Nagaraju, K (Astronomical Society of the Pacific, 2009-06)
    Physical properties of G-band bright points (GBPs) surrounding a pore are studied using observations spanning from photosphere to chromosphere. The magnetic field strengths obtained in these bright points are of the order ...
  • Measurements of seeing-induced crosstalk in tip–tilt corrected solar polarimetry 
    Mathur, Harsh; Nagaraju, K; Pruthvi, Hemanth; Sagayanathan, K (Optica Publishing Group, 2024-05-20)
    We present measurements of seeing-induced crosstalk using spectropolarimetric observations of sunspots recorded simultaneously in the H α and Ca II 8662 Å lines with the Kodaikanal Tower Tunnel (KTT) telescope. The Kodaikanal ...
  • 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 ...
  • On the Variability of the Solar Mean Magnetic Field: Contributions from Various Magnetic Features on the Surface of the Sun 
    Souvik Bose; Nagaraju, K (IOP Publishing, 2018-07-20)
    The solar mean magnetic field (SMMF) is referred to as the disk-averaged line-of-sight (LOS) magnetic field that also reflects the polarity imbalance of the magnetic field on the Sun. The origin of the SMMF has been debated ...
  • On the Weakening of the Chromospheric Magnetic Field in Active Regions 
    Nagaraju, K; Sankarasubramanian, K; Rangarajan, K. E (The American Astronomical Society, 2008-05)
    Simultaneous measurement of line-of-sight (LOS) magnetic and velocity fields at the photosphere and chromosphere are presented. The Fe i line at λ6569 and Hα at λ6563 are used for deriving the physical parameters at ...
  • Properties of shock waves in the quiet-Sun chromosphere 
    Mathur, Harsh; Joshi, Jayant; Nagaraju, K; van der Voort, Luc Rouppe; Bose, Souvik (EDP Sciences, 2022-12)
    Context. Short-lived (100 s or less), sub-arcsec to a couple of arcsec sized features of enhanced brightenings in the narrowband images at the H2V and K2V positions of the Ca ii H&K lines in the quiet Sun are known as ...
  • Simultaneous Spectropolarimetric Observations in the Hα and Ca II 8662Å Lines of an Active Region 
    Mathur, Harsh; Nagaraju, K; Yadav, Rahul; Joshi, Jayant (American Astronomical Society, 2024-08-10)
    We present spectropolarimetric observations of an active region recorded simultaneously in the Hα and the Ca II 8662 Å lines. The sunspot exhibits multiple structures, including a light bridge and a region where the Ca ...
  • Smear correction of highly variable, frame-transfer CCD images with application to polarimetry 
    Iglesias, F. A; Feller, A; Nagaraju, K (Optical Society of America, 2015-07-01)
    Image smear, produced by the shutterless operation of frame-transfer CCD detectors, can be detrimental for many imaging applications. Existing algorithms used to numerically remove smear do not contemplate cases where ...
  • Solar mean magnetic field of the chromosphere 
    Vishnu, M; Nagaraju, K; Mathur, Harsh (Indian Academy of Sciences, 2023-12)
    The Solar Mean Magnetic Field (SMMF) is the mean value of the line-of-sight (LOS) component of the solar vector magnetic field averaged over the visible hemisphere of the Sun. So far, the studies on SMMF have mostly been ...
  • Solar spectropolarimetry of Ca II 8542 Å line: polarimeter development, calibration, and preliminary observations 
    Hemanth, P; Nagaraju, K; Ravindra, B; Ramesh, K. B (SPIE-The International Society for Optical Engineering, 2018-11)
    Chromospheric magnetic fields are of paramount importance in understanding the dynamics of energetic events in the solar atmosphere. At the Kodaikanal Solar Observatory, several polarimeters were developed in the past to ...

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