On the formation of solar wind & switchbacks, and quiet Sun heating

Vishal Upendran

Hosted by Inter-University Center for Astronomy and Astrophysics (IUCAA), India on December 16, 2021


The solar coronal heating in quiet Sun (QS) and coronal holes (CH), including solar wind formation, are intimately tied by magnetic field dynamics. Thus, a detailed comparative study of these regions is needed to understand the underlying physical processes. CHs are known to have subdued intensity and larger blueshifts in the corona. This work investigates the similarities and differences between CHs and QS in the chromosphere using the Mg II h & k, C II lines, and transition region using Si IV line, for regions with identical absolute magnetic flux density (|B|). We find CHs to have subdued intensity in all the lines, with the difference increasing with line formation height and |B|. The chromospheric lines show excess upflows and downflows in CH, while Si IV shows excess upflows (downflows) in CHs (QS), where the flows increase with |B|. We further demonstrate that the upflows (downflows) in Si IV are correlated with both upflows and downflows (only downflows) in the chromospheric lines. CHs (QS) show larger Si IV upflows (downflows) for similar flows in the chromosphere, suggesting a common origin to these flows. These observations may be explained due to impulsive heating via interchange (closed-loop) reconnection in CHs (QS), resulting in bidirectional flows at different heights, due to differences in magnetic field topologies. Finally, the kinked field lines from interchange reconnection may be carried away as magnetic field rotations and observed as switchbacks. Thus, our results suggest a unified picture of solar wind emergence, coronal heating, and near-Sun switchback formation.


  • “On the formation of solar wind & switchbacks, and quiet Sun heating”: Vishal Upendran and Durgesh Tripathi 2021, ApJ (accepted).
  • “Properties of the C II 1334 Å Line in Coronal Hole and Quiet Sun as Observed by IRIS”: Vishal Upendran and Durgesh Tripathi 2021, ApJ, 922, 112
  • “Coronal Heating and Solar Wind Formation in Quiet Sun and Coronal Holes: A Unified Scenario”: Durgesh Tripathi et al. 2021, ApJ, 908, 28

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