Defining the Middle Corona

Matthew J. West, Daniel B. Seaton, David B. Wexler, John C. Raymond, Giulio Del zanna, Yeimy J. Rivera, Adam R. Kobelski, Bin Chen, Craig Deforest, Leon Golub, Amir Caspi, Chris R. Gilly, Jason E. Kooi, Karen A. Meyer, Benjamin L. Alterman, Nathalia Alzate, Vincenzo Andretta, Frédéric Auchère, Dipankar Banerjee, David BerghmansPhillip Chamberlin, Lakshmi Pradeep Chitta, Cooper Downs, Silvio Giordano, Louise Harra, Aleida Higginson, Russell A. Howard, Pankaj Kumar, Emily Mason, James P. Mason, Richard J. Morton, Katariina Nykyri, Ritesh Patel, Laurel Rachmeler, Kevin P. Reardon, Katharine K. Reeves, Sabrina Savage, Barbara J. Thompson, Samuel J. Van kooten, Nicholeen M. Viall, Angelos Vourlidas, Andrei N. Zhukov

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The middle corona, the region roughly spanning heliocentric distances from 1.5 to 6 solar radii, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere. The solar wind, eruptions, and flows pass through the region, and they are shaped by it. Importantly, the region also modulates inflow from above that can drive dynamic changes at lower heights in the inner corona. Consequently, the middle corona is essential for comprehensively connecting the corona to the heliosphere and for developing corresponding global models. Nonetheless, because it is challenging to observe, the region has been poorly studied by both major solar remote-sensing and in-situ missions and instruments, extending back to the Solar and Heliospheric Observatory (SOHO) era. Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased. Although the region cannot be intrinsically separated from other regions of the solar atmosphere, there has emerged a need to define the region in terms of its location and extension in the solar atmosphere, its composition, the physical transitions that it covers, and the underlying physics believed to shape the region. This article aims to define the middle corona, its physical characteristics, and give an overview of the processes that occur there.

Original languageEnglish
Article number78
Number of pages61
JournalSolar Physics
Issue number6
Publication statusPublished - 14 Jun 2023

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