Surface Abundances of Light Elements as Diagnostics of Transport Processes in the Sun and Solar-Type Stars

AbstractObservations of the surface abundances of lithium, beryllium and helium-3 in the Sun and in solar-type stars of different ages should be interpreted in a coherent way. The abundance of lithium at the surface of a star decreases slowly with age; for stars of the same age it decreases with mass and a dependence on the rotation velocity is suggested. The solar surface lithium is depleted by a factor of 100 relative to the cosmic abundance while an He-3 enrichment of 15% at the solar surface during evolution is suggested.Observations favour the hypothesis of a slow transport process at work between the outer convective zone and the radiative interior of these stars. Orders of magnitude of the transport coefficient as well as its dependence upon the physical parameters can be inferred from surface abundances of light elements, but at the moment we are far from producing a completely consistent modelization.

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Rotational Transport Processes

Symposium - International Astronomical Union ◽

10.1017/s0074180900195841 ◽

2004 ◽

Vol 215 ◽

pp. 336-345 ◽

Cited By ~ 1

Author(s):

Suzanne Talon

Keyword(s):

Magnetic Field ◽

Gravity Waves ◽

Meridional Circulation ◽

Chemical Transport ◽

Transport Processes ◽

Momentum Transport ◽

The Sun ◽

Physical Mechanisms ◽

Self Consistent ◽

Solar Type

In this review, I discuss physical mechanisms leading to momentum and chemical transport in stars. Various instabilities leading to turbulence are discussed. I then present a self-consistent description of rotational mixing under the action of turbulence and meridional circulation in 1D models. Limitations of the model are discussed, both in terms of an extra mechanism for momentum transport in the Sun and solar-type stars (magnetic field and/or gravity waves) and in terms of our understanding of turbulent properties.

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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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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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Transforming in-situ observations of CME-driven shock accelerated protons into the shock's reference frame.

Annales Geophysicae ◽

10.5194/angeo-23-1931-2005 ◽

2005 ◽

Vol 23 (5) ◽

pp. 1931-1941 ◽

Cited By ~ 1

Author(s):

I. M. Robinson ◽

G. M. Simnett

Keyword(s):

Solar Physics ◽

Solar Energetic Particle ◽

Transport Processes ◽

Solar Energetic Particle Event ◽

The Sun ◽

Proton Acceleration ◽

Angle Scattering ◽

Peak Energy ◽

In Situ Observations

Abstract. We examine the solar energetic particle event following solar activity from 14, 15 April 2001 which includes a "bump-on-the-tail" in the proton energy spectra at 0.99 AU from the Sun. We find this population was generated by a CME-driven shock which arrived at 0.99 AU around midnight 18 April. As such this population represents an excellent opportunity to study in isolation, the effects of proton acceleration by the shock. The peak energy of the bump-on-the-tail evolves to progressively lower energies as the shock approaches the observing spacecraft at the inner Lagrange point. Focusing on the evolution of this peak energy we demonstrate a technique which transforms these in-situ spectral observations into a frame of reference co-moving with the shock whilst making allowance for the effects of pitch angle scattering and focusing. The results of this transform suggest the bump-on-the-tail population was not driven by the 15 April activity but was generated or at least modulated by a CME-driven shock which left the Sun on 14 April. The existence of a bump-on-the-tail population is predicted by models in Rice et al. (2003) and Li et al. (2003) which we compare with observations and the results of our analysis in the context of both the 14 April and 15 April CMEs. We find an origin of the bump-on-the-tail at the 14 April CME-driven shock provides better agreement with these modelled predictions although some discrepancy exists as to the shock's ability to accelerate 100 MeV protons. Keywords. Solar physics, astrophysics and astronomy (Energetic particles; Flares and mass ejections) – Space plasma physics (Transport processes)

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Boron Behavior During the Evolution of the Early Solar System: The First 180 Million Years

Elements ◽

10.2138/gselements.13.4.231 ◽

2017 ◽

Vol 13 (4) ◽

pp. 231-236 ◽

Cited By ~ 2

Author(s):

Charles K. Shearer ◽

Steven B. Simon

Keyword(s):

Solar System ◽

Solar Nebula ◽

Nuclear Reactions ◽

Terrestrial Planets ◽

The Sun ◽

Planetary Formation ◽

Light Elements ◽

Early Solar System ◽

Spallation Reactions ◽

Magma Oceans

The behavior of boron during the early evolution of the Solar System provides the foundation for how boron reservoirs become established in terrestrial planets. The abundance of boron in the Sun is depleted relative to adjacent light elements, a result of thermal nuclear reactions that destroy boron atoms. Extant boron was primarily generated by spallation reactions. In the initial materials condensing from the solar nebula, boron was predominantly incorporated into plagioclase. Boron abundances in the terrestrial planets exhibit variability, as illustrated by B/Be. During planetary formation and differentiation, boron is redistributed by fluids at low temperature and during crystallization of magma oceans at high temperature.

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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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