uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Properties of small-scale magnetism of stellar atmospheres
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
Show others and affiliations
2014 (English)In: Nippon Tenmon Gakkai obun kenkyu hokoku, ISSN 0004-6264, Vol. 66, no SI1, S5- p.Article in journal (Refereed) Published
Abstract [en]

The magnetic field outside of sunspots is concentrated in the intergranular space, where it forms a delicate filigree of bright ribbons and dots as seen on broad band images of the Sun. We expect this small-scale magnetic field to exhibit a similar behavior in stellar atmospheres. In order to find out more about it, we perform numerical simulations of the surface layers of stellar atmospheres. Here, we report on preliminary results from simulations in the range between 4000 K and 6500 K effective temperature with an initial vertical, homogeneous magnetic field of 50 G strength. We find that the field strength of the strongest magnetic flux concentrations increases with decreasing effective temperature at the height level where the average Rosseland optical depth is one. On the other hand, at the same level, the field is less strong than the thermal equipartition value in the coolest model but assumes superequipartition in the models hotter than 5000 K. While the Wilson depression of the strongest field concentrations is about one pressure scale height in the coolest model, it is more than four times the pressure scale height in the hottest one. We also find that the relative contribution of the bright filigree to the bolometric, vertically directed radiative intensity is most significant for the T-eff = 5000 K model (0.6%-0.79%) and least significant for the hottest and coolest models (0.1%-0.46% and 0.14%-0.32%, respectively). This behavior suggests that the effect of the small-scale magnetic field on the photometric variability is more significant for K dwarf stars than for F-type and also M-type stars.

Place, publisher, year, edition, pages
2014. Vol. 66, no SI1, S5- p.
Keyword [en]
magnetohydrodynamics (MHD), stars: atmospheres, stars: magnetic field
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:uu:diva-245551DOI: 10.1093/pasj/psu083ISI: 000348521000005OAI: oai:DiVA.org:uu-245551DiVA: diva2:792918
Available from: 2015-03-05 Created: 2015-02-26 Last updated: 2015-03-05Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Freytag, Bernd
By organisation
Theoretical Astrophysics
In the same journal
Nippon Tenmon Gakkai obun kenkyu hokoku
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 534 hits
ReferencesLink to record
Permanent link

Direct link