[FLASH-USERS] Checkboard of Magnetic Monopoles

[Aaron Froese]

I am using the USM MHD solver with flash3 and I noticed that I am getting very large magnetic monopoles appearing in my solution, of the same order as the magnetic fields.  The monopoles appear in a somewhat random checkboard-like pattern, which I believe has something to do with the block-structure of the mesh.  I have attached two plots which show the magnitude of divb and posted copies online in case the mailing list does not allow file attachments.

Cylindrical Shell Compression 2D - abs(divb)
http://oi40.tinypic.com/1zeihbp.jpg

Spherical Shell Compression 3D - abs(divb)
http://oi39.tinypic.com/34grldv.jpg

The central circle where the checkboard pattern appears is the only volume that is magnetized.  I am using a static AMR mesh with a uniform resolution across the magnetized volume, and less refinement in the surrounding non-magnetized fluid.  Has anyone observed similar behaviour?  It is definitely numerical in nature, but I do not know what part of the code is responsible.

Thanks,
Aaron
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