Comparative Analysis of the Activity Cycles of the Atmospheres of the Sun and of Stars of the Solar-Type

AbstractObservations of magnetic activity cycles in other stars provide a broader context for our understanding of the 11-year sunspot cycle. The discovery of short activity cycles in a few stars, and the recognition of analogous variability in the Sun, suggest that there may be two distinct dynamos operating in different regions of the interior. Consequently, there is a natural link between studies of magnetic activity and asteroseismology, which can characterize some of the internal properties that are relevant to dynamos. I provide a brief historical overview of the connection between these two fields (including prescient work by Wojtek Dziembowski in 2007), and I highlight some exciting results that are beginning to emerge from the Kepler mission.

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A Search for Dyson Spheres around Late-Type Stars in the Solar Neighborhood II

International Astronomical Union Colloquium ◽

10.1017/s0252921100015281 ◽

1997 ◽

Vol 161 ◽

pp. 707-709 ◽

Cited By ~ 1

Author(s):

Jun Jugaku ◽

Shiro Nishimura

Keyword(s):

Solar Neighborhood ◽

The Sun ◽

Late Type ◽

Solar Type

AbstractWe continued our search for partial (incomplete) Dyson spheres associated with 50 solar-type stars (spectral classes F, G, and K) within 25 pc of the Sun. No candidate objects were found.

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Land, People and Power in Early Medieval Wales: The cantref of Cemais in comparative perspective

10.30861/9781407357126 ◽

2020 ◽

Author(s):

Rhiannon Comeau

Keyword(s):

Comparative Analysis ◽

Urban Society ◽

Comparative Perspective ◽

Seasonal Activity ◽

Early Medieval ◽

Habitual Activity ◽

Activity Cycles

A study of seasonal activity cycles in a pre-urban society, examined through the lens of an early medieval Welsh case study. It examines how these cycles shaped patterns of power and habitual activity, defining spaces and structuring lives. Its multidisciplinary, comparative analysis identifies focal zones and challenges commonly applied interpretations.

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The role of science in the study of and response to space threats

Вестник Российской академии наук ◽

10.31857/s0869-5873898777-799 ◽

2019 ◽

Vol 89 (8) ◽

pp. 777-799

Author(s):

B. M. Shustov

Keyword(s):

Comparative Analysis ◽

20Th Century ◽

21St Century ◽

Space Debris ◽

The Sun ◽

National Program ◽

Biological Hazard ◽

Academy Of Sciences ◽

Space Activities

During the second half of the 20th century and the beginning of the 21st century, space hazards multiplied, the most urgent of which is space debris. Professionals working in space are exposed to this hazard daily and are aware of it as a problem. Furthermore, increasing attention is being paid to the unpredictable behavior of the Sun, which produces the so-called space weather. The asteroid-comet hazard is considered as potentially having the most catastrophic consequences. No manifestations of biological hazard have yet been observed, although as space activities develop, it is becoming increasingly important. The appropriate time scale for astrophysical hazards is many millions of years, so from a practical perspective, they have no importance. This article briefly describes the main types of space hazards. The author analyzes the results of research and practical work in the field, both worldwide and specifically in Russia. Comparative analysis leads to the clear conclusion that a national program must be developed for the study of space hazards and to respond to space threats. This article is based on a report made by the author at the meeting of the Presidium of the Russian Academy of Sciences (RAS) on January 15, 2019.

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Exploring Flaring Behaviour on Low Mass Stars, Solar-type Stars and the Sun

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009980 ◽

2019 ◽

Vol 15 (S354) ◽

pp. 384-391

Author(s):

L. Doyle ◽

G. Ramsay ◽

J. G. Doyle ◽

P. F. Wyper ◽

E. Scullion ◽

...

Keyword(s):

High Energy ◽

The Sun ◽

Low Mass Stars ◽

Highly Active ◽

Rotation Phase ◽

Solar Type ◽

Low Mass ◽

Insight Into ◽

Reconnection Model ◽

High Cadence

AbstractWe report on our project to study the activity in both the Sun and low mass stars. Utilising high cadence, Hα observations of a filament eruption made using the CRISP spectropolarimeter mounted on the Swedish Solar Telescope has allowed us to determine 3D velocity maps of the event. To gain insight into the physical mechanism which drives the event we have qualitatively compared our observation to a 3D MHD reconnection model. Solar-type and low mass stars can be highly active producing flares with energies exceeding erg. Using K2 and TESS data we find no correlation between the number of flares and the rotation phase which is surprising. Our solar flare model can be used to aid our understanding of the origin of flares in other stars. By scaling up our solar model to replicate observed stellar flare energies, we investigate the conditions needed for such high energy flares.

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The frequency of stellar X-ray flares from a large-scale XMM-Newton sample

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316008668 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 134-137

Author(s):

John P. Pye ◽

Simon R. Rosen

Keyword(s):

Solar System ◽

Solar Flare ◽

Space Weather ◽

White Light ◽

Large Scale ◽

The Sun ◽

X Ray ◽

Cool Star ◽

Exoplanetary Systems ◽

Solar Type

AbstractWe present estimates of cool-star X-ray flare rates determined from the XMM-Tycho survey (Pyeet al. 2015, A&A, 581, A28), and compare them with previously published values for the Sun and for other stellar EUV and white-light samples. We demonstrate the importance of applying appropriate corrections, especially in regard to the total, effective size of the stellar sample. Our results are broadly consistent with rates reported in the literature for Kepler white-light flares from solar-type stars, and with extrapolations of solar flare rates, indicating the potential of stellar X-ray flare observations to address issues such as ‘space weather’ in exoplanetary systems and our own solar system.

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Stellar Surface Convection, Line Asymmetries, and Wavelength Shifts

International Astronomical Union Colloquium ◽

10.1017/s0252921100048661 ◽

1999 ◽

Vol 170 ◽

pp. 268-277 ◽

Cited By ~ 5

Author(s):

Dainis Dravins

Keyword(s):

Adaptive Optics ◽

Temporal Variability ◽

Stellar Surface ◽

Time Variability ◽

The Sun ◽

Atmospheric Physics ◽

Spatially Resolved ◽

Activity Cycles ◽

To Come ◽

Surface Convection

AbstractWavelength positions of photospheric absorption lines may be affected by surface convection (stellar granulation). Asymmetries and wavelength shifts originate from correlated velocity and brightness patterns: rising (blueshifted) elements are hot (bright), and convective blueshifts result from a larger contribution of such blueshifted photons than of redshifted ones from the sinking and cooler (darker) gas. For the Sun, the effect is around 300 m s−1, expected to increase in F-type stars, and in giants. Magnetic fields affect convection and induce lineshift variations over stellar activity cycles. A sufficient measuring precision reveals also the temporal variability of line wavelengths (due to the evolution of granules on the stellar surface). A major future development to come from adaptive optics and optical interferometry will be the study of wavelength variations across spatially resolved stars, together with their spatially resolved time variability. Thus, precise radial velocities should soon open up new vistas in stellar atmospheric physics.

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Carrington Events

Annual Review of Astronomy and Astrophysics ◽

10.1146/annurev-astro-112420-023324 ◽

2021 ◽

Vol 59 (1) ◽

Author(s):

Hugh S. Hudson

Keyword(s):

Solar Flare ◽

Coronal Mass Ejection ◽

Cosmic Ray ◽

Lessons Learned ◽

Publication Date ◽

The Sun ◽

Theoretical Understanding ◽

Solar Event ◽

Solar Type ◽

Mass Ejection

The Carrington event in 1859, a solar flare with an associated geomagnetic storm, has served as a prototype of possible superflare occurrence on the Sun. Recent geophysical (14C signatures in tree rings) and precise time-series photometry [the bolometric total solar irradiance (TSI) for the Sun, and the broadband photometry from Kepler and Transiting Exoplanet Survey Satellite, for the stars] have broadened our perspective on extreme events and the threats that they pose for Earth and for Earth-like exoplanets. This review assesses the mutual solar and/or stellar lessons learned and the status of our theoretical understanding of the new data, both stellar and solar, as they relate to the physics of the Carrington event. The discussion includes the event's implied coronal mass ejection, its potential “solar cosmic ray” production, and the observed geomagnetic disturbances based on the multimessenger information already available in that era. Taking the Carrington event as an exemplar of the most extreme solar event, and in the context of our rich modern knowledge of solar flare and/or coronal mass ejection events, we discuss the aspects of these processes that might be relevant to activity on solar-type stars, and in particular their superflares. ▪ The Carrington flare of 1859, though powerful, did not significantly exceed the magnitudes of the greatest events observed in the modern era. ▪ Stellar “superflare” events on solar-type stars may share common paradigms, and also suggest the possibility of a more extreme solar event at some time in the future. ▪ We benefit from comparing the better-known microphysics of solar flares and CMEs with the diversity of related stellar phenomena. Expected final online publication date for the Annual Review of Astronomy and Astrophysics, Volume 59 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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