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Review

Stellar Chromospheric Variability

by 1,2,* and 1,2
1
Department of Physics and Astronomy, Macquarie University, Balaclava Road, Sydney, NSW 2109, Australia
2
Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Balaclava Road, Sydney, NSW 2109, Australia
*
Author to whom correspondence should be addressed.
Academic Editor: Roberto Mignani
Universe 2021, 7(11), 440; https://doi.org/10.3390/universe7110440
Received: 1 October 2021 / Revised: 1 November 2021 / Accepted: 8 November 2021 / Published: 15 November 2021
(This article belongs to the Special Issue Stellar Astrophysics)
Cool stars with convective envelopes of spectral types F and later tend to exhibit magnetic activity throughout their atmospheres. The presence of strong and variable magnetic fields is evidenced by photospheric starspots, chromospheric plages and coronal flares, as well as by strong Ca ii H+K and Hα emission, combined with the presence of ultraviolet resonance lines. We review the drivers of stellar chromospheric activity and the resulting physical parameters implied by the observational diagnostics. At a basic level, we explore the importance of stellar dynamos and their activity cycles for a range of stellar types across the Hertzsprung–Russell diagram. We focus, in particular, on recent developments pertaining to stellar rotation properties, including the putative Vaughan–Preston gap. We also pay specific attention to magnetic variability associated with close binary systems, including RS Canum Venaticorum, BY Draconis, W Ursae Majoris and Algol binaries. At the present time, large-scale photometric and spectroscopic surveys are becoming generally available, thus leading to a resurgence of research into chromospheric activity. This opens up promising prospects to gain a much improved understanding of chromospheric physics and its wide-ranging impact. View Full-Text
Keywords: stellar chromospheres; stellar atmospheres; magnetic variable stars; solar cycle; stellar magnetic fields; late-type stars stellar chromospheres; stellar atmospheres; magnetic variable stars; solar cycle; stellar magnetic fields; late-type stars
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MDPI and ACS Style

de Grijs, R.; Kamath, D. Stellar Chromospheric Variability. Universe 2021, 7, 440. https://doi.org/10.3390/universe7110440

AMA Style

de Grijs R, Kamath D. Stellar Chromospheric Variability. Universe. 2021; 7(11):440. https://doi.org/10.3390/universe7110440

Chicago/Turabian Style

de Grijs, Richard, and Devika Kamath. 2021. "Stellar Chromospheric Variability" Universe 7, no. 11: 440. https://doi.org/10.3390/universe7110440

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