[FLASH-USERS] Z-pinch equilibrium simulation

[Zahra Seifollahi Moghadam]

Dear FLASH users,

We have recently used FLASH MHD module for 2-D cylindrical (R-Z) simulation
of Z-pinch equilibrium. We have initialized our simulation with Bennett
equilibrium profiles for density and magnetic field and zero velocity all
over the domain. More details in the following reference:

K. Tummel et al., “Kinetic simulations of sheared flow stabilization in
high-temperature Z-pinch plasmas,” Physics of Plasmas, vol. 26, no. 6, p.
062506, Jun. 2019, doi: 10.1063/1.5092241.

We have used periodic BC for inlet and outlet, axisymmetric BC for r=0, and
reflecting BC for r=Rmax. When we ran our simulation without any
perturbation seed. Even though we expected to see a stable pinch for the
whole simulation time and velocity remaining zero, the pinch was only
stable and in equilibrium for some time and we observed growing
instabilities and an increase in radial velocity from zero to factors of
Alfven velocity. We attached two snapshots for t=0 and t=16 us of the
simulations we ran to clearly illustrate the problem.

We are wondering what could be the source of this problem and how this
problem could be possibly mitigated?

Any comment and help are highly appreciated.

Thanks,
Zahra Seifollahi
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