University of Dundee MHD Group 
Postdoctoral Fellow Simon Candelaresi 

Movies
Driven magnetic field carpet for an isothermal atmosphere. The field lines on the left panel are tracing the magnetic field where the color denotes the strength of the magnetic field, the red spheres mark the locations of the magnetic nulls and the color at the lower boundary denotes the zcomponent of the magnetic field. Simulation done in a 256*256*256 box for resistive MHD with the PencileCode.
The visualization was made with Paraview.
Download in higher resolution: skeleton_para_sharp_e3_u005_nu4e3_damping_n256.m4v
[ arXiv:1611.03325 ]
Ideal relaxation of an initially twisted magnetic field with net twist 0. The initially twisted field undergoes an evolution which reduces the free magnetic energy and the strength of the Lorenz force resulting in a forcefree state of minimal energy.
The upper left corner shows the magnetic streamlines, lower left a volume rendering of the magnetic energy and the two panels on the right show the deformation of the grid.
To simulate the nonresistive relaxation we use the magnetofrictional equations for the evolution and apply linetied boundary conditions. The code used is GLEMuR, a finite difference simulation software which uses Lagrangian grid methods, mimetic numerical operators and runs on GPUs.
The visualization was made with Paraview.
Download in higher resolution: bfield_stokes_pon_65_pi_2_eps0_zUp1_p32_lines.avi
[ arXiv:1405.0942 ]
Helical smallscale turbulent motions lead to an enhancement of magnetic energy. First the smallscale field grows then the field of the largest scale. Due to the conservation of magnetic helicity the largescale field grows only on resistive time scales.
left: volume rendering of the zcomponent of the magnetic field
right: loglog plot of the power spectrum for the magnetic energy
Simulations in a 128**3 triply periodic box with a helical forcing, which is random in time. The nonrelativistic MHD equaitons for an isothermal gas are solved with the PencilCode.
Download in higher resolution: bz_128_kf_15_a.mpg
[ arxiv:1208.4529 ]
2D hydrodynamics simulation of a Kolmogorov flow with high Reynolds number. A small initial disturbance in the velocity field gets increased by the instability. The colors represent vorticity.
Simulation done in a 512*512*1 box for resistive hydrodynamics with the PencileCode.
Download in higher resolution: kolmogorov_highRe.mpg
2D hydrodynamics simulation of a Kolmogorov flow with low Reynolds number. A small initial disturbance in the velocity field gets increased by the instability. The colors represent vorticity.
Simulation done in a 256*128*1 box for resistive hydrodynamics with the PencileCode.
Download in higher resolution: kolmogorov_lowRe.mpg
Magnetic field lines in a simulation with the Borromean rings as initial magnetic field configuration. The colors represent the magnitude of the field. At the end of the simulations two separated helical structures appear. Their magnetic helicity is of opposite sign. Simulation done in a 256*256*256 box for resistive MHD with the PencileCode.
Download in higher resolution: borromean_fieldlines.mpg
[ Phys. Rev. E, 84(1):016406, 2011 ]
Magnetic field lines in a simulation with a IUCCA knot as initial magnetic field configuration. The colors represent the magnitude of the field. At the end of the simulations two separated helical structures appear. Their magnetic helicity is of opposite sign. Simulation done in a 256*256*256 box for resistive MHD with the PencileCode.
Download in higher resolution: iucaa_256a.mpg
[ Phys. Rev. E, 84(1):016406, 2011 ]
Magnetic field lines in a simulation with a 4foil knot as initial magnetic field configuration. The colors represent the magnitude of the field. The topology of the system is preserved in form of internal twist. Simulation done in a 128*128*128 box for resistive MHD with the PencileCode.
Download in higher resolution: video_fieldlines_4foil.mpg
[ Phys. Rev. E, 84(1):016406, 2011 ]
Magnetic field lines in a simulation with a trefoil knot as initial magnetic field configuration. The colors represent the magnitude of the field. The topology of the system is preserved in form of internal twist. Simulation done in a 128*128*128 box for resistive MHD with the PencileCode.
Download in higher resolution: trefoil_128a1_fluxtubes.mpg
[ Phys. Rev. E, 84(1):016406, 2011 ]
Volume rendering of the magnetic energy for a simulation with a trefoil knot as initial magnetic field configuration. Simulation done in a 128*128*128 box for resistive MHD with the PencileCode.
Download in higher resolution: trefoil_128a1_vdf.mpg
[ Phys. Rev. E, 84(1):016406, 2011 ]
Magnetic field lines in a simulation with three interlocked flux rings and zero magnetic helicity. The colors represent the magnitude of the field. The topology of the system gets apparently destroyed. Simulation done in a 256*256*256 box for resistive MHD with the PencileCode.
Download in higher resolution: H0_256d2.mpg
[ Phys. Rev. E, 81:036401, 2010 ]
Magnetic field lines in a simulation with three interlocked flux rings and finite magnetic helicity. The colors represent the magnitude of the field. The topology of the system is conserved. Note the twist of the inner ring as the outer rings reconnect. This reflects helicity conservation. Simulation done in a 256*256*256 box for resistive MHD with the PencileCode.
Download in higher resolution: H4_256d2.mpg
[ Phys. Rev. E, 81:036401, 2010 ]