Sunspots and MHD

ChaosKnight · Post by **ChaosKnight** » Sat Mar 15, 2008 9:50 am

Can anybody tell me how to numerically solve the equations for a problem involving magnetohydrodynamics? Specifically to model the emergence of sunspots and their associated arch filaments.

Post by **rcj** » Sat Mar 15, 2008 10:37 am

you may like to subscribe to the MHA journal (http://mhd.sal.lv/)? Is this for your school project? Frankly, I am not sure of any existing model that one could use for sunspots on the Sun, although it would have been a great MHA candidate since it is hot plasma-based and has a large magnetic Reynolds number, and a consistent magnetic field within the fluid. But it would be challenging to model it since we cannot change any experimental parameters, what more, we cannot see what is within. Nevertheless, do keep this thread updated of any findings, this is quite interesting. One useful thing that may come up of this is the prediction of the start and end of solar cycles based on the polarity fluctuations of leading and following sunspots, and this is certainly MHD-based in character.

ChaosKnight · Post by **ChaosKnight** » Sat Mar 15, 2008 9:59 pm

MHD have been applied to sunspots. The guys at the Earth Simulator have been doing it for sometime. Check these out:

http://www.es.jamstec.go.jp/publication ... -isobe.pdf
http://www.es.jamstec.go.jp/publication ... sumoto.pdf

i know that MHD problems are difficult, and this thread will likely not turn up anything. But for a start, what i'd like to know is whether anyone knows any solving schemes for a typical MHD problem. Means solving:

1. Navier Stokes equations in 3-D. Or preferably just the compressible Euler equations
2. Continuity equation
3. Equation of state, since this is a compressible problem
4. Energy equation
5. All the 4 Maxwell equations
6. Any other necessary equations that i still don't know about
Plus any discretization and coupling schemes. Any help with HPC/MPI resources will be good too.

And no, this is not for any school project. No school for me since i dropped out of poly few months ago.

Cheryl · Post by **Cheryl** » Thu Mar 20, 2008 8:57 am

Waah super cheem. Chaos are u really a poly dropout?? Hahaa~~

ChaosKnight · Post by **ChaosKnight** » Thu Feb 26, 2009 9:02 pm

Finally got started on this. i think i have figured out the fluid part.

This is a simulation of a cubic fluid domain subjected to different temperatures at the top and bottom. The navier-stokes and temperature diffusion-advection equations are solved.

The loops are stream traces showing convection rolls. Now we have to figure out how to get an array of such rolls, and how to incorporate maxwell's equations.

ChaosKnight · Post by **ChaosKnight** » Sun Mar 22, 2009 9:22 pm

Got sidetracked abit, an aerospace application for the fluid solver. Simulation of flapping wing flight.

superiorstream · Post by **superiorstream** » Mon Mar 23, 2009 8:02 am

Hi,Everybody,
So much for those good work and mathematical solution for those equations and 3-D generated diagrams.For one thing, I dont think we after Five thousands years of civilisation really even come to the real understanding of the real reason for sunspot formation and prominences.;and thats why observing the sun is so interesting;with lots of surprises.
Take this as an example-there are many more--:It is observed that there are many prominences that levitate in the sun "atmosphere" for hours without changing shape and as admitted, no body understand how this is achieved. If we do then, we have perhaps tame fusion and produce energy from sea water's hydrogen.I love to shot such levitating prominences using my solarmax 90.They take all kinds of funny unpredictible shapes!(see:-www.chia-astroblog.blogspot.com)
Sunspots and solar flare are even worse-example-the present sunspot min is supose to end last april(2008)-but we instead are at the deepest minimun of all;with even prominences show dulling out.Totally unpredictitable.
What we can do is to enjoy the show that come forth and try to shot more good pic of the sun!Thanks

ChaosKnight · Post by **ChaosKnight** » Fri Mar 27, 2009 9:45 pm

Haha. Yes i've seen the many ways people regard simulation results. I'm only a layman in this field, but allow me to share some examples.

The first kind are the highly technical people. They look at the plots, then ask "These plots are nice, but are they correct?" These people are highly critical of what they see, and are near impossible to fool. However these people are also the most forgiving, in the sense they understand the technical limitations of computer models. They know when good work = only qualitative results and when good work = highly accurate quantitative results.

Then there are the "executive" kind, who, when presented with colourful pictures, will make polite noises and comment how impressive or how cool they are. They don't really understand what goes on, and are afraid of asking questions that make them look silly. Or they are not really interested. And weird these are mostly the local "executives". The foreign "executives" i see are engineers who work their way up, and usually fall in the first category.

The third kind are the most interesting. These are ignorant folks who don't understand technical issues behind the numerics. They often say things like "It is only a simulation, not real, therefore should be dismissed as wrong/useless" , but what they are actually saying is "The technical issues here are beyond me, but i must voice my opinion somehow to appear intelligent, and i will do it by criticizing in the most vague way possible." I've seen engineers tear these people apart like tissue paper. Or get so disgusted they simply ignore them during the Q&A, leaving them standing at the microphone. Quite entertaining to watch, really.

In any case, here's the criticism of someone experienced with computer models: http://resources.zdnet.co.uk/articles/c ... 474,00.htm

ChaosKnight · Post by **ChaosKnight** » Sat May 16, 2009 11:50 am