Untitled

Badalyan, O. G.; Livshits, M. A.; Sýkora, J.

doi:10.1023/a:1004984021245

Cited by 22 publications

(20 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Most wind models can be divided roughly into two categories: those that try to apply existing knowledge of the physics of the solar wind to other stars (Cranmer & Saar 2011;Suzuki et al 2013), and those that scale the solar wind to other stars by assuming scaling relations between wind properties and stellar parameters, such as age, rotation rate, or coronal X-ray properties (e.g. Badalyan & Livshits 1992;Grießmeier et al 2004;Holzwarth & Jardine 2007;See et al 2014). An example of the latter type of model was used by Grießmeier et al (2004Grießmeier et al ( , 2007.…”

Section: Stellar Winds In Theory and Practicementioning

confidence: 99%

Stellar winds on the main-sequence

Johnstone

Güdel

Lüftinger

et al. 2015

A&A

100

View full text Add to dashboard Cite

Aims. We develop a method for estimating the properties of stellar winds for low-mass main-sequence stars between masses of 0.4 M and 1.1 M at a range of distances from the star. Methods. We use 1D thermal pressure driven hydrodynamic wind models run using the Versatile Advection Code. Using in situ measurements of the solar wind, we produce models for the slow and fast components of the solar wind. We consider two radically different methods for scaling the base temperature of the wind to other stars: in Model A, we assume that wind temperatures are fundamentally linked to coronal temperatures, and in Model B, we assume that the sound speed at the base of the wind is a fixed fraction of the escape velocity. In Paper II of this series, we use observationally constrained rotational evolution models to derive wind mass loss rates. Results. Our model for the solar wind provides an excellent description of the real solar wind far from the solar surface, but is unrealistic within the solar corona. We run a grid of 1200 wind models to derive relations for the wind properties as a function of stellar mass, radius, and wind temperature. Using these results, we explore how wind properties depend on stellar mass and rotation. Conclusions. Based on our two assumptions about the scaling of the wind temperature, we argue that there is still significant uncertainty in how these properties should be determined. Resolution of this uncertainty will probably require both the application of solar wind physics to other stars and detailed observational constraints on the properties of stellar winds. In the final section of this paper, we give step by step instructions for how to apply our results to calculate the stellar wind conditions far from the stellar surface.

show abstract

Section: Stellar Winds In Theory and Practicementioning

confidence: 99%

Stellar winds on the main-sequence

Johnstone

Güdel

Lüftinger

et al. 2015

A&A

100

View full text Add to dashboard Cite

show abstract

“…Many papers investigate the polarization degree of coronal radiation. Here, we will mention only a few works (van de Hulst, 1950;Molodensky, 1973;Koutchmy, Picat, and Dantel, 1977;Nikolsky, Sazanov, and Kishonkov, 1977;Durst, 1982;Koutchmy, 1994;Kim et al, 1996;Badalyan, Livshits, and Sykora, 1997;Badalyan and Sykora, 2008), describing several eclipses. Notice that there are very few papers that present P K (R) distributions deduced from brightness measurements of the white-light corona only (see van de Hulst, 1950;Durst, 1982, for example).…”

Section: The Degree Of the K-corona Polarization And Total Degree Of mentioning

confidence: 99%

“…Various P K (R) radial dependencies (presented in the first approximation in the figures on the left) limit regions within which the true distributions of the degree of the K-corona polarization are found. Figure 7 presents the distributions of the total polarization degree P KF (R) at the equator, streamer, saddle and pole, with the P KF (R) distributions obtained in the streamer and polar region during the eclipse of 30 June 1973 (Koutchmy, Picat, and Dantel, 1977;Badalyan, Livshits, and Sykora, 1997), shown as well for comparison. Notice the clear difference (especially at the pole) between the total polarization degrees obtained by two research teams when observing the same eclipse of 30 June 1973.…”

Section: The Degree Of the K-corona Polarization And Total Degree Of mentioning

confidence: 99%

White-Light Observations and Polarimetric Analysis of the Solar Corona During the Eclipse of 1 August 2008

et al. 2011

View full text Add to dashboard Cite

In order to study the solar corona during eclipses, a new telescope was constructed. Three coronal images were obtained simultaneously through a single objective of the telescope as the coronal radiation passed through three polarizers (whose transmission directions were turned 0°, 60°, and 120°in the chosen direction); one image was obtained without a polarizer. The telescope was used to observe the solar corona during the eclipse of 1 August 2008. We obtained the distributions of polarization brightness, K-corona brightness, the degree of K-corona polarization and the total polarization degree; the polarization direction, depending on the latitude and radius in the plane of the sky, was also obtained. We calculated the radial distributions of electron density depending on the latitude. The properties of all these distributions were compared for different coronal structures. We determined the temperature of the coronal plasma in different coronal structures assuming hydrostatic equilibrium.

show abstract

“…As far as we know, all observations of the 530.3 nm emission corona (also known as the green-light corona) have previously been based on the use of a single filter centered at the line in question (e.g. Badalyan & Sýkora 1997). Moreover, it was assumed that the contribution from the white-light corona, which had to be subtracted, is the same everywhere.…”

Section: The Green-line and 284 Nm Euv Coronamentioning

confidence: 99%

Comparing eclipse observations of the 2008 August 1 solar corona with an MHD model prediction

Rusin¹,

Druckmüller

Aniol³

et al. 2010

A&A

View full text Add to dashboard Cite

Context. The structure of the white-light and emission solar coronas and their MHD modelling are the context of our work. Aims. A comparison is made between the structure of the solar corona as observed during the 2008 August 1 total eclipse from Mongolia and that predicted by an MHD model. Methods. The model has an improved energy formulation, including the effect of coronal heating, conduction of heat parallel to the magnetic field, radiative losses, and acceleration by Alfvén waves. Results. The white-light corona, which was visible up to 20 solar radii, was of an intermediate type with well-pronounced helmet streamers situated above a chain of prominences at position angles of 48, 130, 241, and 322 degrees. Two polar coronal holes, filled with a plethora of thin polar plumes, were observed. High-quality pictures of the green (530.3 nm, Fe XIV) corona were obtained with the help of two narrow-passband filters (centered at the line itself and the vicinity of 529.1 nm background), with a FWHM of 0.15 nm. Conclusions. The large-scale shape of both the white-light and green corona was found to agree well with that predicted by the model. In this paper we describe the morphological properties of the observed corona, and how it compares with that predicted by the model. A more detailed analysis of the quantitative properties of the corona will be addressed in a future publication.

show abstract

Untitled

Cited by 22 publications

References 3 publications

Stellar winds on the main-sequence

Stellar winds on the main-sequence

White-Light Observations and Polarimetric Analysis of the Solar Corona During the Eclipse of 1 August 2008

Comparing eclipse observations of the 2008 August 1 solar corona with an MHD model prediction

Contact Info

Product

Resources

About