Abstract Details
| Name: Hirdesh Kumar Affiliation: Udaipur Solar Observatory, Physical Research Laboratory Conference ID: ASI2024_484 Title : Study of the Evolution of Velocity and Magnetic Fields in the Solar Atmosphere Authors and Co-Authors : Hirdesh Kumar Abstract Type : Oral Abstract Category : Thesis Abstract : Solar atmosphere provides a conducive environment for the generation, propagation, mode-conversion, and dissipation of various MHD waves. The 5-min oscillations appearing on the solar photosphere are due to the acoustic waves which are generated in the convection zone of the Sun, via turbulent convection and are trapped in the acoustic cavities formed inside the Sun. These acoustic oscillations are suppressed in the strong magnetic regions due to the inhibition of convection. However, solar flares are known to excite these oscillations in the sunspots. During the solar flares, abrupt changes in Lorentz force can also induce seismic emission in the sunspots. Moreover, the trapped low-frequency acoustic waves beneath the solar photosphere are considered to leak along the inclined magnetic fields due to reduction in cut-off frequency. The slow-magnetoacoustic waves are known to propagate along the magnetic field with increasing amplitude, while fast magnetoacoustic waves are refracted above β = 1 layer, and downward propagating waves are known to cause high-frequency acoustic halos surrounding strong magnetic concentrations. The internal or atmospheric gravity waves in the Sun are generated by the buoyancy force and are also recognized as an important contributor to the dynamics and energetics of the lower solar atmosphere. While propagating energy upwards, their characteristics negative phase shift over height is a well-recognized observational signature. However, the propagation of these waves in the magnetized structures shows that these waves are scattered/suppressed and refracted, suggesting that the propagation of gravity waves is hampered in the presence of magnetic fields. In this thesis, we have investigated the evolution of velocity and magnetic fields in the solar atmosphere with an emphasis to understand the propagation of waves in the lower solar atmosphere, utilizing data obtained from various space-based (SDO, RHESSI, and GOES) and ground-based solar observing facilities (MAST, IBIS/DST, and GONG). |