Stellar flares

Abstract Magnetic storms on stars manifest as remarkable, randomly occurring changes of the luminosity over durations that are tiny in comparison to the normal evolution of stars. These stellar flares are bursts of electromagnetic radiation from X-ray to radio wavelengths, and they occur on most sta...

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Main Author: Adam F. Kowalski
Format: Article
Language:English
Published: Springer 2024-04-01
Series:Living Reviews in Solar Physics
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Online Access:https://doi.org/10.1007/s41116-024-00039-4
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author Adam F. Kowalski
author_facet Adam F. Kowalski
author_sort Adam F. Kowalski
collection DOAJ
description Abstract Magnetic storms on stars manifest as remarkable, randomly occurring changes of the luminosity over durations that are tiny in comparison to the normal evolution of stars. These stellar flares are bursts of electromagnetic radiation from X-ray to radio wavelengths, and they occur on most stars with outer convection zones. They are analogous to the events on the Sun known as solar flares, which impact our everyday life and modern technological society. Stellar flares, however, can attain much greater energies than those on the Sun. Despite this, we think that these phenomena are rather similar in origin to solar flares, which result from a catastrophic conversion of latent magnetic field energy into atmospheric heating within a region that is relatively small in comparison to normal stellar sizes. We review the last several decades of stellar flare research. We summarize multi-wavelength observational results and the associated thermal and nonthermal processes in flaring stellar atmospheres. Static and hydrodynamic models are reviewed with an emphasis on recent progress in radiation-hydrodynamics and the physical diagnostics in flare spectra. Thanks to their effects on the space weather of exoplanetary systems (and thus in our search for life elsewhere in the universe) and their preponderance in Kepler mission data, white-light stellar flares have re-emerged in the last decade as a widely-impactful area of study within astrophysics. Yet, there is still much we do not understand, both empirically and theoretically, about the spectrum of flare radiation, its origin, and its time evolution. We conclude with several big-picture questions that are fundamental in our pursuit toward a greater understanding of these enigmatic stellar phenomena and, by extension, those on the Sun.
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spelling doaj-art-4190e87e64634ddeb55b801e0fb4ad0e2024-12-22T12:30:15ZengSpringerLiving Reviews in Solar Physics1614-49612024-04-01211115710.1007/s41116-024-00039-4Stellar flaresAdam F. Kowalski0Department of Astrophysical and Planetary Sciences, University of ColoradoAbstract Magnetic storms on stars manifest as remarkable, randomly occurring changes of the luminosity over durations that are tiny in comparison to the normal evolution of stars. These stellar flares are bursts of electromagnetic radiation from X-ray to radio wavelengths, and they occur on most stars with outer convection zones. They are analogous to the events on the Sun known as solar flares, which impact our everyday life and modern technological society. Stellar flares, however, can attain much greater energies than those on the Sun. Despite this, we think that these phenomena are rather similar in origin to solar flares, which result from a catastrophic conversion of latent magnetic field energy into atmospheric heating within a region that is relatively small in comparison to normal stellar sizes. We review the last several decades of stellar flare research. We summarize multi-wavelength observational results and the associated thermal and nonthermal processes in flaring stellar atmospheres. Static and hydrodynamic models are reviewed with an emphasis on recent progress in radiation-hydrodynamics and the physical diagnostics in flare spectra. Thanks to their effects on the space weather of exoplanetary systems (and thus in our search for life elsewhere in the universe) and their preponderance in Kepler mission data, white-light stellar flares have re-emerged in the last decade as a widely-impactful area of study within astrophysics. Yet, there is still much we do not understand, both empirically and theoretically, about the spectrum of flare radiation, its origin, and its time evolution. We conclude with several big-picture questions that are fundamental in our pursuit toward a greater understanding of these enigmatic stellar phenomena and, by extension, those on the Sun.https://doi.org/10.1007/s41116-024-00039-4Stellar flaresSolar flaresOptical flaresStellar atmospheres
spellingShingle Adam F. Kowalski
Stellar flares
Living Reviews in Solar Physics
Stellar flares
Solar flares
Optical flares
Stellar atmospheres
title Stellar flares
title_full Stellar flares
title_fullStr Stellar flares
title_full_unstemmed Stellar flares
title_short Stellar flares
title_sort stellar flares
topic Stellar flares
Solar flares
Optical flares
Stellar atmospheres
url https://doi.org/10.1007/s41116-024-00039-4
work_keys_str_mv AT adamfkowalski stellarflares