[FLASH-USERS] Biermann Battery in 2D and 3D geometry

[Xavier Ribeyre]

Dear FLASH Code users, 

In the FLASH version 4.6.2 there is two Biermann battery test cases. 
One in 2D cartesian geometry and one in 2D axis-symmetric (cylindrical) geometry. 

1- Whatever in 2D Cartesian or 2D axis-symmetric cases: the magnetic z component is the same. 
And there is no magnetic field variation whatever I activated the 
"source BB terms" or the "3T BB term": i.e in flash.par: 
(use_Biermann3T = .false. hy_biermannSource = .true. 
or use_Biermann3T = .true. hy_biermannSource = .false.) 
The z component values of the magnetic field magz are the same. This behavior is correct. 

-However it seems that the SIGN of the magz component is not correct in 2D axis-symmetric case (it is the opposite). 
Are you agree with that? 

2- I did the same test case in 3D geometry with the the same temperature and density profile. 

When I deactivated the source term 
i.e. use_Biermann3T = .true. hy_biermannSource = .false. in the flash.par 
The values of magz seems correct (if we compare with the 2D previous cases) 
BUT 
When Biermann source term is activated: 
i.e. use_Biermann3T = .false. hy_biermannSource = .true. in flash.par 
then now the magz values are very different and very low (20 times lower). 

-I don't know why there is a discrepancy between these two 3D simulations 

I hope you can help to understand what happens. 

Best regards, 

Xavier Ribeyre 



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