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Browsing by Subject "Sun: Oscillations"

Browsing by Subject "Sun: Oscillations"

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  • Accelerating waves in polar coronal holes as seen by EIS and SUMER 
    Gupta, G. R; Banerjee, D; Teriaca, L; Imada, S; Solanki, S (IOP Science, 2010-07-20)
    We present EIS/Hinode and SUMER/SOHO observations of propagating disturbances detected in coronal lines in inter-plume and plume regions of a polar coronal hole. The observation was carried out on 2007 November 13 as part ...
  • Alfven waves in a gravitational field with flows 
    Satya Narayanan, A; Kathiravan, C; Ramesh, R (Cambridge University Press, 2009-03)
    The gravitational stratification effect on magnetohydrodynamic waves at a single interface in the solar atmosphere has been studied in the penumbral region of the sunspot recently. The existence of slow and fast magneto ...
  • Comparison of GONG and MDI sound-speed anomalies beneath two active regions 
    Hughes, S. J; Rajaguru, S. P; Thompson, M. J (European Space Agency, 2004-10)
    Travel times of acoustic waves are calculated from Dopplergrams of solar oscillations obtained using the Global Oscillation Network Group (GONG) ground-based network and the Michelson Doppler Imager (MDI) instrument on ...
  • Dynamics and heating of the magnetic network on the Sun. Efficiency of mode transformation 
    Hasan, S. S; Ulmschneider, P (EDP Sciences, 2004-12)
  • Dynamics of the Solar Magnetic Network: Two-dimensional MHD Simulations 
    Hasan, S. S; van Ballegooijen, A. A; Kalkofen, W; Steiner, O (The American Astronomical Society, 2005-10)
    The aim of this work is to identify the physical processes that occur in the network and contribute to its dynamics and heating. We model the network as consisting of individual flux tubes, each with a nonpotential field ...
  • Excitation of Longitudinal Modes in Solar Magnetic Flux Tubes by p-Modes 
    Hasan, S. S; Kalkofen, W (Astronomical Society of the Pacific, 1998)
    This is a continuation of earlier work by Hasan (1997) on the interaction of longitudinal (sausage) waves in a slender flux tube with p-modes in the ambient medium. We use a realistic stratification for the flux tube and ...
  • Excitation of Oscillations in the Magnetic Network on the Sun 
    Hasan, S. S; Kalkofen, W; van Ballegooijen, A. A (The American Astronomical Society, 2000-05)
    We examine the excitation of oscillations in the magnetic network of the Sun through the footpoint motion of photospheric magnetic flux tubes located in intergranular lanes. The motion is derived from a time series of ...
  • GONG p-mode frequency changes with solar activity 
    Bhatnagar, A; Jain, K; Tripathy, S. C (Astronomical Society of India, 2000)
    In this paper, we present a correlation study of nine solar activity indices with p-mode frequency shifts obtained from the GONG data. It is found that the two are closely correlated and a linear relationship exits. Further, ...
  • Inferring the chromospheric magnetic topology through waves 
    Hasan, S. S; Steiner, O; van Ballegooijen, A (Cambridge University Press, 2008-05)
    The aim of this work is to examine the hypothesis that the wave propagation time in the solar atmosphere can be used to infer the magnetic topography in the chromosphere as suggested by Finsterle et al. (2004). We do this ...
  • The Influence of a Vertical Magnetic Field on Oscillations in an Isothermal Stratified Atmosphere. II. 
    Banerjee, D; Hasan, S. S; Christensen-Dalsgaard, J (University of Chicago Press, 1995-10)
    We examine the effect of a uniform vertical magnetic field on the modes of an isothermal stratified atmosphere. The present investigation is a continuation of earlier work by Hasan & Christensen-Dalsgaard in which this ...
  • Kink and Longitudinal Oscillations in the Magnetic Network on the Sun: Nonlinear Effects and Mode Transformation 
    Hasan, S. S; Kalkofen, W; van Ballegooijen, A. A; Ulmschneider, P (The American Astronomical Society, 2003-03)
    We examine the propagation of kink and longitudinal waves in the solar magnetic network. Previously, we investigated the excitation of network oscillations in vertical magnetic flux tubes through buffeting by granules and ...
  • The Linear Response of a Magnetic Flux Tube to Buffeting by External p-Modes. I 
    Hasan, S. S (The American Astronomical Society, 1997-05)
    The linear response of a thin vertical magnetic flux tube to buffeting by p-modes in the ambient atmosphere is examined with the aim of understanding the interaction of acoustic modes with sausage tube waves. The idealized ...
  • Metric observations of transient, quasi-periodic radio emission from the solar corona in association with a ``halo'' CME and an ``EIT wave'' event 
    Ramesh, R; Kathiravan, C; Satya Narayanan, A; Ebenezer, E (The European Southern Observatory, 2003-03)
    We present metric radio observations of quasi-periodic emission from the solar corona in close association with a ``halo'' CME and an ``EIT wave'' phenomenon. The radio event lasted for about 60 s. Its mean periodicity was ...
  • On the flare induced high-frequency global waves in the sun 
    Kumar, B; Mathur, S; García, R. A; Venkatakrishnan, P (Institute of Physics, 2010-03-01)
    Recently, Karoff & Kjeldsen presented evidence of strong correlation between the energy in the high-frequency part (5.3 < ν < 8.3 mHz) of the acoustic spectrum of the Sun and the solar X-ray flux. They have used disk-integrated ...
  • Processes in the magnetized chromosphere of the Sun 
    Hasan, S. S (Cambridge University Press, 2009-03)
    We review physical processes in magnetized chromospheres on the Sun. In the quiet chromosphere, it is useful to distinguish between the magnetic network on the boundaries of supergranules, where strong magnetic fields are ...
  • Propagating waves in polar coronal holes as seen by SUMER & EIS 
    Banerjee, D; Teriaca, L; Gupta, G. R; Imada, S; Stenborg, G; Solanki, S. K (EDP Sciences, 2009-06)
    Context: To study the dynamics of coronal holes and the role of waves in the acceleration of the solar wind, spectral observations were performed over polar coronal hole regions with the SUMER spectrometer on SoHO and the ...
  • Ring Diagram Analysis of the Characteristics of Solar Oscillation Modes in Active Regions 
    Rajaguru, S. P; Basu, S; Antia, H. M (The American Astronomical Society, 2001-12)
    The presence of intense magnetic fields in and around sunspots is expected to modify solar structure and oscillation frequencies. Applying the ring diagram technique to data from the Michelson Doppler Imager on board the ...
  • Rotation rate and flows in the solar interior 
    Antia, H. M (Astronomical Society of India, 2000)
    The rotation rate in the solar interior can be inferred from measured splittings of solar oscillation frequencies using various inversion techniques. While other large scale flows can be studied using local techniques, ...
  • The seismic sun 
    Basu, S (Astronomical Society of India, 2000)
    The "Seismic Sun" is a model of the Sun constructed using helioseismological deductions about the Sun. The seismic Sun is very similar to a standard solar model which incorporates gravitational settling of helium and heavy ...
  • Signatures of Alfven waves in the polar coronal holes as seen by EIS/Hinode 
    Banerjee, D; Perez-Suarez, D; Doyle, J. G (2009-06-26)
    Context. We diagnose the properties of the plume and interplume regions in a polar coronal hole and the role of waves in the acceleration of the solar wind. Aims. We attempt to detect whether Alfven waves are present in ...

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