On the coupling between lower and upper atmosphere of the Sun

Abstract

The thesis is focused on the study of the small-scale transients and waves as seen in the different layers of the solar atmosphere and the coupling between the different layers. The unique high resolution data obtained by the newly launched Interface Region Imaging Spectrograph (IRIS) is used to study the highly dynamic, less understood, chromosphere and transition region and their dynamical connection with the corona. The Atmospheric Imaging Assembly (AIA) images onboard the Solar Dynamics Observatory (SDO) cover a broad range of temperature in the corona. The Helioseismic and Magnetic Imager magnetogram (HMI) onboard the SDO has helped us to study the evolution of the magnetic eld at the photosphere. The high-resolution data from the the Swedish 1-m Solar Telescope (SST) equipped with the CRISP Imaging SpectroPolarimeter is used to study the photosphere and the chromosphere. The chromospheric data obtained from the Solar Optical Telescope (SOT) onboard Hinode is also used. High spatial resolution, high time cadence, simultaneous imaging and spectroscopic coordinated observational data as recorded from these instruments are used to study the dynamics of different fine structures, small-scale transients events and their responses in the different layers of the solar atmosphere. The interaction between magnetohydrodynamics (MHD) waves and inclined magnetic fields is explored in a quiet-Sun region. Small-scale transient like mottles, Rapid Blueshifted Excursions (RBEs), and Rapid Redshifted Excursions (RREs) in the chromosphere are studied and their coupling through the photosphere to upper chromosphere is also studied. Small- scale chromospheric and transition regions jets, e.g., Type I and Type II spicules, are ubiquitously found in the solar atmosphere. In this thesis we explored the connec- tion between these jets and the dynamical changes observed in the coronal structures, e.g., coronal bright points and, coronal plumes. The fine-structure dynamics above the sunspot are also explored. The relation between the subarcsecond bright dots in the transition region and the micro-jets in the chromosphere are explored to find their formation mechanism. We have also studied the \high-frequency oscillations" in the coronal structure as observed during a total solar eclipse from the Easter Island, Chile. The characterization of these \high-frequency waves", their importance in the coronal heating and the damping mechanisms are explored. Thus, through the dynamical study of various transients, the coupling between the different layers of the solar atmosphere is studied while using high spatial and temporal resolution data in multi wavelengths as recorded from different space based and ground based imaging and spectroscopic instruments.