Abstract Details

Name: Avyarthana Ghosh
Affiliation: Inter-University Center for Astronomy and Astrophysics
Conference ID: ASI2021_366
Title : Spectroscopic Studies of Plasma Flows in Active Regions in the Transition Region
Authors and Co-Authors : Avyarthana Ghosh (IUCAA) Durgesh Tripathi (IUCAA) James A. Klimchuk (NASA Goddard Space Flight Center)
Abstract Type :
Abstract Category : Sun and the Solar System
Abstract : The transition region is the most dynamic amongst the layers of the solar atmosphere. Earlier studies on Doppler flows in the strong field regions of active regions showed dominant redshifts whereas the corridors separating them were reported to have blueshifts, for all disk positions. Similarly, the non-thermal velocities in active regions were attributed to a variety of causes- waves, turbulence, plasma flows associated with nanoflares, to name a few. However, the non-thermal velocities were reported to have some center-to-limb variation (CLV), most likely due to opacity effects. In this work, we use the very high resolution spectroscopic data for the Si IV 1393.77 Å line from the Interface Region Imaging Spectrograph, coupled with magnetic field images from the Helioseismic Magnetic Imager onboard the Solar Dynamic Observatory to ascertain the role of magnetic fields in plasma flows in the transition region active regions. We report that the strong field regions have predominant redshifts whereas the corridors have two populations- a central region with near-zero velocities and another redshifted population, adjacent to the strong field boundaries. In both cases, there is a modest hint to a CLV. For non-thermal velocities too, we note a high-speed component at the strong field regions, whereas there is a narrow strip in the corridor with substantially lower non-thermal velocities, with no convincing CLV. Based on our Doppler velocity observations, we conclude that the Si IV emission comes primarily from Type II spicules, which are obscured by the cooler Type I spicules. At the same time, the non-thermal velocities are attributed to unresolved flows along the field lines, instead of waves or turbulence.