Dynamic wave-modes in solar chromospheric structures

• Main Author: Sharma, Rahul
• Other Authors: von-Fay Siebengurgen, Robertus ; Verth, Gary
• Published: University of Sheffield 2017
• Subjects: 510
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.749468

Sun’s outer atmosphere is a million degree hotter than it’s visible surface, which is not understood with any of the known laws of thermodynamics and remains an intriguing problem for the astrophysics in general. It is now believed that most of the energy dissipation phenomenon occurs at the interface-region, which is a highly dynamic, gravitationally stratified, nonlinear, inhomogeneous environment, where the plasma-β varies from large, across unity, to very small. Previous studies, suggests that energy from lower solar atmosphere is transported up higher in corona by waves and oscillations through small-scale thin magnetic flux-tube structures, that populate the interface-region. This thesis primarily focuses on the identification and the understanding of the coupled linear/nonlinear wave-modes that are confined in the observed flux-tube structures. High-resolution imaging-spectroscopy data from the ground-based telescope is used to get an unprecedented view of the spicule structures within the complex chromospheric environment. Innovative analysis techniques were developed, for the first time, to investigate the three-dimensional (3D) ensemble of the observed kinematic components. The subsequent analysis at both, pixel- and the tube-scale, provided important insight into the nonlinear evolution of the coherent wave-modes, along with their consequent affects on the ambient solar atmosphere. Key findings include, the accurate interpretation of the observed spectroscopic (Doppler) velocity profiles, which were akin for both torsional Alfvén and kink wave modes. It was shown that the kinematic behavior of the kink wave-mode is not entirely transverse, but also has associated rotational component, due to displaced surrounding plasma. Also, the various observed kinematic components (transverse, cross-sectional width, azimuthal torsion) which, till-date, were observed independent to each other were found strongly coupled, with definitive phase-relationships. Furthermore, the non- helical evolution of the coupled dynamical components across the interface region, was found, due to the presence of a plethora of nonlinear wave phenomenon. The analysis, presented in this thesis, on the dynamics in the solar chromosphere, can provide the vital clues and insight into the mechanisms responsible for the transfer and dissipation of energy.