Abstract Details

Name: Sajal Kumar Dhara
Affiliation: Udaipur Solar Observatory/Physical Research Laboratory
Conference ID: ASI2017_1331
Title : Study of Evolution of Magnetic Inhomogeneities on the Sun using Narrow Band Imaging
Authors and Co-Authors :
Abstract Type : Thesis
Abstract Category : Thesis
Abstract : The solar atmosphere is structured by the evolving magnetic fields. On small scale - bright points with thin boundaries have been observed. On large spatial scale - plages, sunspots and filaments/prominences have been observed. One such magnetic structure is solar filament which contain dense and cool plasma embedded in the tenuous and hot corona. They appear above a boundary between the opposite polarity of magnetic fields on the Sun, normally called as polarity inversion line. They normally form in active regions, though not very uncommon in quiet regions. The quiet filament structures are highly stable and most of them will survive for weeks to months. On the other hand, the active region filaments evolve rapidly and they can survive over a period varying from few hours to days. Most often, the filament ends up with eruption associated with solar flares and CMEs. In this thesis I have studied a few selected active region filament eruptions using high resolution coronal data from AIA/SDO and ground based Hα data from BBSO and GONG to examine and understand the detailed mechanism behind these filament eruptions. The study suggests that in each filament event the onset of trigger and instability mechanism could be different. In one event, we concluded that the progress of events towards eruption, is broadly consistent with flux cancellation, that subsequently erupts due to onset of a runaway tether cutting magnetic reconnection. In other event, we found that the emerging flux, converging motion and injection of opposite magnetic helicity could be responsible for destabilizing of the filament leading towards its eruption. The observations made in multiple wavelengths around a chromospheric spectral line could provide valuable data to infer dynamical processes occur such as converging motions and rotational motions in the ends of the filaments during the eruption. We observed the rotational/vortical motion in the photosphere near the ends of the several erupting active region filaments during their initial phase of eruption, at the onset of the fast rise phase. The observed vortical motions are about supergranulation size and lasted for 4–29 minutes. Another work of this thesis is to develop a narrow band imager using Fabry-Perot interferometer, which can provide images at the chromospheric height in the solar atmosphere and also it is capable of producing dopplergrams at this height using some post-facto techniques, to study the line-of-sight motions during the filament eruptions. Here, I will present the important results obtained in this thesis work and discuss the summary and conclusion of the work along with a brief descriptions of planned future projects in which research can be carried out further.