Stellar Convection Properties

[Tech Sgt. Chen]

In Ref. To: http://www.shatters.net/forum/viewtopic.php?t=8072

I've just begun reading a Conference summary from the IAU Symposium titled "How Are We Doing So Far? A summary of the Symposium." by M. M. Dworetsky, Dept. of Physics and Astronomy, University College London.
The link to this paper is here: http://www.star.ucl.ac.uk/~mmd/Dworetsky-summary224.ps

A paragraph taken out of context (Page 3, Section 7 "Advances In Modelling Convection") reads, "The discussion of new simulations of convection in A stars began with the paper by Freytag. The cells are expected to be much larger on A stars than on the Sun. Convective motions, up and down, can be modelled and may produce something that looks like microturbulance."
Now, I know this is discussing A stars and that the strong hydrogen lines in A stars may contribute to the large convection cells.

Additionally, I located an interesting article strongly supporting the presence of stellar spots (some that cover 50% of the surface) in hot stars where none were previously believed to exist.
http://www.space-art.co.uk/markgarlick/articles/f_articles2.htm?skytel_starspots
This article emphasizes the direct correlation of spot sizes to star rotation speeds rather than, star size or temperature.

Another good article called, "Why are the Stars in the Pleiades so Blue?"
at:http://www2.si.edu/research/spotlight/1_25.htm#pleiades
describes the Pleiades as young, blue, fast rotating stars that have many "sunspots".

These, along with the M. Schwartzschild theory (1975) that convection cells on giant stars are large and their number limited, are some of the resources from which I draw inferences in creating my star textures.
It would seem logical that probabilities also exist to support that Blue Supergiants display convection or radiactive type cells based on these references.
I certainly would appreciate any links that refute my current inferences. If I'm going to make star textures, I want to do it correctly!

[eburacum45]

Since that paper mentions the work by Freytag which I have been looking at, I thought I'd better go back and check the simulations again; turns out I was looking at them wrong.
In fact I was wrong about convection cells being smaller in hotter stars, so I apologise.
Here is the page I was looking at with respect to convection cell size; you have to look at each movie in turn
http://www.astro.uu.se/~bf/movie/movie.html

you will see in the simulation that the cell size appears to get smaller as the star gets hotter; but what I did not look at was the scale along the bottom. The scale for the A-class stars is much larger than that for the G and K class stars.

So I read the simulations completely wrong; I apologise.
Nevertheless the Red Giant simulations do certainly show gigantic, slow moving convection cells, as I remembered.

The convention zone is smaller in hotter main sequence stars, I believe; but detailed modelling as done by Freytag et al shows that the cells actually get larger in A-class stars.

[Malenfant]

While we're getting technical, can someone tell me how sunspot size is supposed to be related to convection cell size (if it even is at all)? That's the implication I got from the 'blue supergiant' thread - I always thought sunspot size was determined by magnetic field lines and strength, and had nothing to do with convection cells.

[Tech Sgt. Chen]

Malenfant wrote:

can someone tell me how sunspot size is supposed to be related to convection cell size (if it even is at all)?

I've updated/edited my original post here (above). From my understanding of the sizes of sunspots/stellar spots, I get the impression that they're governed strictly by the star's individual, magnetic properties alone. These magnetic properties are varied and as individual to stars as personalities to people. Even as far as certain groups of people are catagorized in Sociology, these magnetic properties can also be applied to certain groups of stars. One of the influences that has a great effect on these magnetic properties is the star's rotational speed.

eburacum45 wrote:

So I read the simulations completely wrong; I apologise

No apology necessary. I often make mistakes while reading or researching references, especially when trying to comprehend after getting home from work at 6:15AM in the morning and having started work at 6:00PM the night before.
If it were not for the questions you guys ask or the points you bring up, I would not be able to properly research my work. I do thank you all sincerely. Your questions help me to complete my work!