Stellar Chromospheric Variability

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 <span sty...

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Autores principales:	Richard de Grijs, Devika Kamath
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	stellar chromospheres stellar atmospheres magnetic variable stars solar cycle stellar magnetic fields late-type stars Elementary particle physics QC793-793.5
Acceso en línea:	https://doaj.org/article/5c563de4bbe3431baeb89943d64414bf
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spelling	oai:doaj.org-article:5c563de4bbe3431baeb89943d64414bf2021-11-25T19:09:48ZStellar Chromospheric Variability10.3390/universe71104402218-1997https://doaj.org/article/5c563de4bbe3431baeb89943d64414bf2021-11-01T00:00:00Zhttps://www.mdpi.com/2218-1997/7/11/440https://doaj.org/toc/2218-1997Cool 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 <span style="font-variant: small-caps;">ii</span> H+K and H<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> 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.Richard de GrijsDevika KamathMDPI AGarticlestellar chromospheresstellar atmospheresmagnetic variable starssolar cyclestellar magnetic fieldslate-type starsElementary particle physicsQC793-793.5ENUniverse, Vol 7, Iss 440, p 440 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	stellar chromospheres stellar atmospheres magnetic variable stars solar cycle stellar magnetic fields late-type stars Elementary particle physics QC793-793.5
spellingShingle	stellar chromospheres stellar atmospheres magnetic variable stars solar cycle stellar magnetic fields late-type stars Elementary particle physics QC793-793.5 Richard de Grijs Devika Kamath Stellar Chromospheric Variability
description	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 <span style="font-variant: small-caps;">ii</span> H+K and H<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> 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.
format	article
author	Richard de Grijs Devika Kamath
author_facet	Richard de Grijs Devika Kamath
author_sort	Richard de Grijs
title	Stellar Chromospheric Variability
title_short	Stellar Chromospheric Variability
title_full	Stellar Chromospheric Variability
title_fullStr	Stellar Chromospheric Variability
title_full_unstemmed	Stellar Chromospheric Variability
title_sort	stellar chromospheric variability
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/5c563de4bbe3431baeb89943d64414bf
work_keys_str_mv	AT richarddegrijs stellarchromosphericvariability AT devikakamath stellarchromosphericvariability
_version_	1718410217843064832

Stellar Chromospheric Variability

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