Celestia Forums

Howdy folks.

I finally found an interesting configuration of a magnetic field which simulates very well solar flares. Here's a picture of a real solar flare that I wanted to represent in Celestia :



Using Mathematica, it was actually extremely difficult (at least to me) to find some nice configuration of field lines which gives something like on the picture above, since they tend to behave in a cahotic way. A small variation of parameters (there are LOTS of them) could change dramatically the field global character. Starting from some "initial conditions" which draw a field line, you can't predict where the line will end or what will be its extent in space. Since there are so much parameters to control (dipole strengh, dipoles number, dipoles position and orientation in space, number of field lines to draw, field line "initial condition", etc), I was at the point to kill the whole project, until I got this nice result today. So here's a complete rotation around the model (anticlock way rotation, as seen from above). Don't worry about the colors, they will be changed at a later stage :























My Mathematica notebook which created this model is a complete mess ! I'll have to do some code cleaning and optimisation before doing the final model.

Of course, the star texture need to be changed to place the sun's spots at a proper location.

Here are more pictures of the real thing, which inspired me :









I absolutely love the last three pictures ! The field lines are so clear on them ! Here's a video showing the typical time evolution of the real magnetic field lines :

http://www.nasa.gov/centers/goddard/mpg ... 20x240.mpg

Just another picture of the prototype model, with more field lines :

the hair are growing on the head :



I'm adding the color variations along the lines :

I don't know what you guys think of this model, but I believe it isn't bad. Of course, once finished, the flares will be placed on some stars (maybe the Sun), instead of that orange balloon.

Will this be animated like the other solar flare addon?


Nice work by the way!

LordFerret wrote:Will this be animated like the other solar flare addon?

Nope. Unfortunately, it's impossible to do in Celestia. Anyway, field lines like these are evolving slowly, compared to ejected matter. Just watch again the movie at the end of my first post.

The main problem with the other flares addon is that it isn't accurate. The flares are moving much too fast. And while you rotate around the flares, you can feel it's a texture mapped on a curved mesh. The flares I'm doing are a bit more "natural", i.e closer to what is shown on the pictures above. The best would be to use the new sprites features of Celestia 1.5, but currently it isn't working on the Mac.

I've watched the movie. I've also seen several others just like it in the past from regular visits to the NASA SOHO site... fascinating stuff.

I'm trying to motivate the curiosity of people here about magnetism. Here's a nice video showing magnetism in action on the Sun :

http://trace.lmsal.com/POD/movies/12520 ... 40x480.mpg

There are lots of fascinating pictures here :

http://trace.lmsal.com/POD/TRACEpodoverview.html

And as a bonus, here's a nice animation showing the field of the star V374 Peg :

http://www.ast.obs-mip.fr/users/donati/ ... ra_mov.gif

I'd never seen the TRACE site before, nice images. I've bookmarked the homepage.

I noticed a few of the LASCO images there. From time to time I visit their site (LASCO's) to check out their real-time and near-real-time imagery. One of the things I've wondered (please pardon my ignorance on this) is for example on the LASCO C3 images - the dark bar which extends from the center occluding disk to the edge.
Example here - http://lasco-www.nrl.navy.mil/cgi-bin/latest_img.cgi?c3+jpg24
Is that part of a device which holds that center occluding disk in place, or the 'wake' of Sol as it moves through space?

I'll also note that, in watching LASCO movies, there seems to be a large amount of "debris" zipping about out there.

Cham wrote:

LordFerret wrote:Will this be animated like the other solar flare addon?

Nope. Unfortunately, it's impossible to do in Celestia.

Animation is possible in Celestia v1.5.0. ScriptedOrbit and ScriptedOrientation functions can be used to move Meshes.

Martin,

Nope. Unfortunately, it's impossible to do in Celestia. Anyway, field lines like these are evolving slowly, compared to ejected matter. Just watch again the movie at the end of my first post.

How about letting e.g. the other physicists in our community know from time to time what you exactly did in your Mathematica calculations.

What were your boundary conditions, for example?? Apparently, you restricted yourself to static solutions? Of which approximation of Maxwell's equations??

etc.

Thanks,
Bye Fridger

PS: You might e.g. publish your well commented Mathematica code in HTML or PDF format, as I do regularly with my more extensive Maple computations for Celestia.

I can follow such things very easily, for example, since besides my theoretical physics expertise, I speak both Maple and Mathematica most fluently...

Cham, it's not bad, it's awesome!

Selden, I hope that these new directives will be collected in a .PDF. I'm unable to find otherwise that a generic quote of Bodyfixed...

Fenrit,

They're described in the Celestia WikiBook.
Look in the sections about "Trajectories" and "Rotation Models".
http://en.wikibooks.org/wiki/Celestia#Customization

I'm using them to animate my model of the Orion spacecraft. I'll make a video available shortly. It's still a work-in-progress.

I apologize, Selden. I do not have see it. Thank you.

Fridger,

this field is the result of a static multi-dipoles distribution (a solution to Maxwell's equations, using linear superposition of simple solutions). Each dipole, tangent to the surface and below it, simulates a pair of sun spots. However, a pair of dipoles gives much better results. All dipoles are placed below the surface, very close to it. I've experimented up to 8 dipoles, distributed on the surface of an unit sphere. Unfortunately, the results are almost impossible to control, since there are too many variables to handle (parameters) : dipole strenght, dipole orientation, dipole location on the sphere, number of field lines to draw and selection of field lines (or initial condition to "grow" the field lines). Most of the time, the field's global aspect is a total mess. So I had to "cheat" a bit : I build a "generic" model using two dipoles only, and placed several of these on the surface, as shown above.

I also intend to simulate the "flux tubes" of entangled field lines, like the small one visible on the center of this image :

http://www.answers.com/topic/traceimage-jpg

In this case, I'm clearly cheating by using knotted curves on a deformed torus. Here's a test model below (unfinished) :



I'm still not sure I'll use this, however.

The Mathematica code is pretty messy right now, especially since I have to select the field lines by hand after inspection (you can't predict the results before the simulation). I'll give some basic parts of the code in my next post. I also programmed Mathematica to cut the curves in 50 parts to add the color variations.


Selden,

I can't make animated curves in Celestia, since they are deforming in an organic way (torsion, etc), if the multi-dipolar source is changing. Of course, the models are fixed to the surface and rotates with it like a rigid body.

t00fri wrote:How about letting e.g. the other physicists in our community know from time to time what you exactly did in your Mathematica calculations.

PS: You might e.g. publish your well commented Mathematica code in HTML or PDF format, as I do regularly with my more extensive Maple computations for Celestia.

For the mathematical inclined, here's a PDF file showing parts of the current field construction process, with Mathematica :

http://nho.ohn.free.fr/celestia/Cham/Divers/field.pdf (200 KB)

This file is divided in several parts :

- Various field definitions, parameters, etc.
- Numerical solution of the field lines, using some constraints, field line selection, etc.
- Graphical inspector, to see if the field configuration is right (most of the time, it isn't !).
- CMOD building block, to export to a TEXT file. The content of the exported file is properly formated for a CMOD. I just need to copy/paste into a CMOD file with its material definitions header and that's all !
- Various experimental stuff, curves manipulation. In this case, I'm deforming a torus and drawing some entangled curves on it.

Please take note that this is experimental stuff. I made several "notebooks" like this one, to build all sorts of curves, dots distributions, fields, etc.

Thanks, Martin,

looking forward to going through this.

I was guessing already that you probably have placed static dipoles under the solar surface. What else?


Bye Fridger

Fridger,

I hope you're not expecting me to solve the full scale MHD equations, isn't ?

multi-dipoles under the carpet is enough.

What do you think of that flux tube (with proper color variations) ?



Edit : here's an example of a possible mess, with a distribution of 5 dipoles :

While the previous multi-dipolar models are okay, I'll investigate another way of doing the magnetic field from the solar spots. I'll treat each spot as a magnetic "monopole", instead of a dipole. This is reasonable, since the other pole is actually hidden deep inside the sun.

Fridger,

I have cleaned the Mathematica code a bit, in the PDF document given above. I also resampled the pictures embeded in it, so the file is now much smaller (200 KB, instead of 720 KB).

Same link :

http://nho.ohn.free.fr/celestia/Cham/Divers/field.pdf