Structure, dynamics and heating in magnetized regions of solar atmosphere G. Vigeesh and S. S. Hasan [Ph.D Thesis]
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TextPublication details: Bangalore Indian Institute of Astrophysics 2010Description: [various pagings.]Subject(s): Online resources: Dissertation note: Doctor of Philosophy University of Mangalore, Mangalore 2010 Summary: The solar variability at UV and EUV wavelengths is dominated by emissions from the “magnetic networks”. These network elements are thought to be heated by dissipation of magneto-hydrodynamic (MHD) waves, but the MHD processes involved in wave generation, propagation and dissipation are only poorly understood. As part of this thesis work, we carried out an investigation of MHD wave dynamics in magnetic network elements using numerical simulations. The work is performed in the context of a model of magnetic network elements as a collection of smaller flux tubes that merge at some height in the chromosphere. Most small-scale magnetic flux concentrations are visible as bright objects with a magnetic field strength in the order of kilogauss, with a typical size of 100 km and a field that is largely vertically oriented. We have carried out a number of numerical simulations of wave propagation in a two dimensional gravitationally stratified atmosphere consisting of individual magnetic flux concentrations. We have studied MHD wave propagation in these structures in order to understand mode coupling and to estimate the energy transported by these waves. These simulations show that the nature of the modes excited depends on the value of plasma (the ratio of gas to magnetic pressure) of the region where the excitation takes place. Mode conversions and transmissions occur in the region where B = 1 and energy is exchanged between various MHD modes. From a rough estimate of the acoustic energy flux generated by such impulsive transverse motions, we conclude that this flux would hardly balance the chromospheric energy requirements in the network. We have also explored the feasibility of developing diagnostic tools for the helioseismic exploration of such atmospheres using numerical simulations. In summary, this thesis aims at contributing to a better understanding of the dynamics of
the magnetic network in the solar atmosphere, which has wider implications in the study of solar and stellar activity.
| Item type | Current library | Shelving location | Call number | Status | Date due | Barcode |
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Thesis & Dissertations
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IIA Library-Bangalore | General Stacks | (043.2):523.9-852/ VIG (Browse shelf(Opens below)) | Available | 18824 |
Doctor of Philosophy University of Mangalore, Mangalore 2010
The solar variability at UV and EUV wavelengths is dominated by emissions from the “magnetic networks”. These network elements are thought to be heated by dissipation of magneto-hydrodynamic (MHD) waves, but the MHD processes involved in wave generation, propagation and dissipation are only poorly understood. As part of this thesis work, we carried out an investigation of MHD wave dynamics in magnetic network elements using numerical simulations. The work is performed in the context of a model of magnetic network elements as a collection of smaller flux tubes that merge at some height in the chromosphere. Most small-scale magnetic flux concentrations are visible as bright objects with a magnetic field strength in the order of kilogauss, with a typical size of 100 km and a field that is largely vertically oriented. We have carried out a number of numerical simulations of wave propagation in a two dimensional gravitationally stratified atmosphere consisting of individual magnetic flux concentrations. We have studied MHD wave propagation in these structures in order to understand mode coupling and to estimate the energy transported by these waves. These simulations show that the nature of the modes excited depends on the value of plasma (the ratio of gas to magnetic pressure) of the region where the excitation takes place. Mode conversions and transmissions occur in the region where B = 1 and energy is exchanged between various MHD modes. From a rough estimate of the acoustic energy flux generated by such impulsive transverse motions, we conclude that this flux would hardly balance the chromospheric energy requirements in the network. We have also explored the feasibility of developing diagnostic tools for the helioseismic exploration of such atmospheres using numerical simulations. In summary, this thesis aims at contributing to a better understanding of the dynamics of
the magnetic network in the solar atmosphere, which has wider implications in the study of solar and stellar activity.
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