Monday, 17/05/2021

Axel Brandenburg: “Scientific usage of the Pencil Code”  [Slides


Jörn Warnecke: “Small-scale dynamo action at very small magnetic Prandtl numbers in the Sun – some of the largest Pencil-Code simulations”

The Sun exhibits magnetic fields on various scales ranging from the size of the star all the way down to the smallest observable scales and probably below. The small-scale magnetic field can be generated by a small-scale dynamo instability (SSD). The very low magnetic Prandtl number (Pm) in the Sun, however, challenges the existence of the SSD, as previous numerical studies have shown that the critical magnetic Reynolds number (Rm) for its excitation increases with decreasing Pm. We present here a numerical study investigating the SSD at lower Pm than studied previously, using numerical simulations of forced turbulence with fluid Reynolds number (Re) up to 40.000 and a resolution of 4096^3 grid points. We found that the critical Rm first increases as a function of decreasing Pm, but then starts decreasing again: SSD can still be excited with a Pm of 0.005 and Rm of around 180. The increase and later decrease of the critical Rm for low Prandtl numbers in our simulations can be explained by the bottleneck effect, an effect where the kinetic power spectrum has a local maximum between the inertial and dissipative scale. Our study predicts that the SSD in the Sun should be easier to excite than previously thought.


Toma Chaumont Behrs: “Chiral inverse cascade of magnetic energy in a relativistic plasma”

The Hubble tension and other cosmological discrepancies call for a better, more complete understanding of the primordial plasma. To this end, the magnetic field, a macroscopic quantum effect related to the chirality of fermions, and relativistic effects are included in the theoretical description of early-Universe plasma physics. Numerical chiral magnetohydrodynamics (χMHD) simulations are run using Pencil Code with both relativistic and non-relativistic equations of state. A chiral dynamo is instigated, and its driving parameter varied to explore different regimes. Time series data and energy spectra (both magnetic and kinetic) are then presented and analysed. In all relativistic runs, the magnetic field drives a smaller velocity field as compared to the non-relativistic runs (due to a difference of a factor of 3/4 in the Lorentz force term of the Navier-Stokes equation). Generally, effects on magnetic field evolution in the turbulent runs are observed, where the velocity field exerts a back-reaction on the magnetic field. A stronger chiral dynamo, i.e. a scenario in which the depletion of the dynamo source term is less efficient, dramatically accelerates the chiral inverse cascade of magnetic energy.


Sahel Dey: “MHD simulations of dynamic Solar atmosphere”


Naveen Jingade: “Proposal to measure the correlation time of helicity fluctuations in shear dynamo simulations”   [Slides]


Frederick Gent: “Intermittency in multiphase astrophysical dynamos” [Slides]


Carolina Ortiz: “Simulations of fully convective M dwarf stars”   [Slides]  


Johannes Tschernitz: “A 2D solar convection simulation”


Yutong He: “Studying Gravitational Waves with the Pencil Code”   [Slides]


Vartika Pandey: “Settling motions in 1D stratification model of the solar corona”  [Slides]


Tuesday, 18/05/2021


Hongzhe Zhou: “Shear current effect I”    [Slides]


Maarit Käpylä: “Shear current effect II” 


Matthias Rheinhardt: “Compressible Testfield Method”   [Slides]


Jörn Warnecke: “Investigating global convective dynamos with mean-field models: full spectrum of turbulent effects required”   [Slides]


Chao-Chin Yang: “The Streaming Instability with Multiple Dust Species in Protoplanetary Disks”

The streaming instability in a system of gas and dust has been playing an important role in our understanding of planetesimal formation in protoplanetary disks. I will discuss my recent works on the linear phase and nonlinear saturation of the streaming instability using multiple dust species with the Pencil Code.


Wednesday, 19/05/2021


Simon Candelaresi: “Numerical Viscosity and Diffusion in Finite Difference Eulerian Codes”    [Slides]


Philippe Bourdin: “Advances in IO and compilation configuration”   [Slides]

We will shortly present the current state of HDF5 IO and discuss possibilities for future improvements and new IO strategies using HDF5. Also some improvements to “pc_build” will be shown, like the automatic switching between MPI, nompi, HDF5 and no HDF5.


Alberto Roper Pol: “Recent results on gravitational waves using the Pencil Code”


Illa R. Losada: “Let there be documentation!”   [Slides]


Thursday, 20/05/2021


Petri Käpylä: “Star-in-a-box simulations of partially and fully convective stars”  [Slides]

I will discuss an updated version of the star-in-a-box setup and recent results regarding dynamos in partially and fully convective stars.


Friday, 21/05/2021


Nishant K. Singh: “3D numerical experiments of magneto-helioseismology”


Johannes Pekkilä: “Status of GPU solvers”   [Slides]