Confined pseudo-shocks as an energy source for the active solar corona

Abstract

The Sun’s active corona requires an energy flux of ~103 W m−2 to compensate for radiative losses and to maintain its high temperature1. Plasma moves in the corona through magnetic loops2,3, which may be connected with the flows in and around sunspots4,5,6. Global energizing processes (for example, reconnection) play an important part in heating the corona7,8,9; however, energy and mass transport may also occur via shocks, waves or flows5,10,11. A full picture and the influence of such localized events, which significantly couple with various layers of the solar upper atmosphere, is still not clear. Using the Interface Region Imaging Spectrograph temporal image data of C ii 1,330 Å, we observed the presence of pseudo-shocks around a sunspot. Unlike shocks12, pseudo-shocks exhibit discontinuities only in the mass density. A two-fluid numerical simulation reproduces such confined pseudo-shocks with rarefied plasma regions lagging behind them. We find that these pseudo-shocks carry an energy of ~103 W m−2, which is enough to locally power the inner corona and also generate bulk flows (~10−5 kg m−2 s−1), contributing to the localized mass transport. If they are ubiquitous, such energized and bulky pseudo-shocks above active regions could provide an important contribution to the heating and mass transport in the overlying solar corona.

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Fig. 1: Direct imaging of the confined pseudo-shocks around a sunspot.
Fig. 2: Evolution of a pseudo-shock.
Fig. 3: Two-fluid simulations of a pseudo-shock using newly developed JOANNA code15.
Fig. 4: Total energy and mass fluxes (for protons + electrons and hydrogen atoms) in a pseudo-shock.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

A.K.S. and B.N.D. acknowledge the RESPOND-ISRO (DOS/PAOGIA205-16/130/602) project. A.K.S. acknowledges the SERB-DST project (YSS/2015/000621) grant, and the Advanced Solar Computational and Analyses Laboratory (ASCAL). Armagh Observatory and Planetarium is grant-aided by the Northern Ireland Department for Communities. J.G.D. acknowledges the DJEI/DES/SFI/HEA Irish Centre for High-End Computing for provision of computing facilities and support. J.G.D. also thanks the STFC for PATT travel and subsistence and the SOLARNET project, which is supported by the European Commission’s FP7 Capacities Programme under grant agreement number 312495, for travel and subsistence. M.S. acknowledges support from ‘Progetti di ricerca INAF di Rilevante Interesse Nazionale’ (PRIN-INAF 2014) and project 2012P2HRCR ‘Il sole attivo ed i suoi effetti sul clima dello spazio e della terra’ (PRIN MIUR 2012) grants, funded by the Italian National Institute for Astrophysics (INAF) and Ministry of Education, Universities and Research (MIUR), respectively. Work by K.M., B.K. and D.P.W. was supported financially by projects at the National Science Centre, Poland (grant numbers 2014/15/B/ST9/00106 and 2017/25/B/ST9/00506). T.V.Z. was supported by the Austrian Science Fund ‘FWF’ project P30695-N27 and Georgian Shota Rustaveli National Science Foundation project DI-2016-17. Z.E.M. acknowledges support from the Alexander von Humboldt Foundation. The authors express thanks to A. Kaczmarczyk for assistance with creating the Adobe illustrations. They also acknowledge the use of IRIS and Solar Dynamics Observatory/Atmospheric Imaging Assembly observations in this work.

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A.K.S. led the project by defining the novel science case, analysing and making the IRIS observations, and writing the paper. K.M., B.K. and D.P.W. constructed the numerical model based on the two-fluid JOANNA code, which was developed by D.P.W. All co-authors (A.K.S., K.M., B.N.D., J.G.D., T.V.Z., M.S., Z.E.M., B.K., D.P.W. and P.K.) participated in studying the science and editing the draft.

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Correspondence to Abhishek Kumar Srivastava.

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Srivastava, A.K., Murawski, K., Kuźma, B. et al. Confined pseudo-shocks as an energy source for the active solar corona. Nat Astron 2, 951–956 (2018). https://doi.org/10.1038/s41550-018-0590-1

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