Name: Vishal Upendran
Affiliation: Inter University Centre for Astronomy and Astrophysics
Conference ID : ASI2022_154
Title : Chromospheric and transition region dynamics in coronal holes and quiet sun
Authors : Vishal Upendran (IUCAA, Pune); Durgesh Tripathi (IUCAA, Pune).
Abstract Type: Poster
Abstract Category : Sun and the Solar System
Abstract : Coronal holes (CHs) are regions with reduced intensity and enhanced blueshifts when compared to Quiet Sun (QS) regions at coronal temperatures, with differences in transition region (TR) seen only for regions with similar magnetic flux density (|B|). In this work, we study the chromospheric Mg II h&k, the C II 1334 Å and TR Si IV line in CHs and QS as a function of |B|. We find the intensities and velocities of all lines increase with |B|. For both the chromospheric lines, we find reduced intensity, excess blueshifts and excess redshifts in CHs over QS for regions with similar |B|. In the Si IV line, CHs show excess blueshifts, but reduced intensity and redshift. On cross-correlating chromospheric and TR velocities, we find (a). Upflows, downflows in all the lines are tightly correlated. (b). Chromospheric upflows are not correlated with TR downflows. (c). Chromospheric downflows are correlated with TR upflows. The TR upflows (downflows) are preferentially larger in CHs (QS) for similar chromospheric flows. These results may be explained through impulsive heating in a stratified atmosphere causing larger upflow (downflow) acceleration (deceleration) in CHs (QS), with the impulsive event giving rise to bidirectional flows. The patterns of observed flows and intensities, may be explained by invoking interchange (closed loop) reconnection in CHs (QS). These results provide evidence on the formation of solar wind in the chromosphere and further hints towards the unified heating scenario of the solar corona in the QS and CHs.