Afterlive: A performant code for Vlasov-Hybrid simulations

A parallelized implementation of the Vlasov-Hybrid method [Nunn, 1993] is presented. This method is a hybrid between a gridded Eulerian description and Lagrangian meta-particles. Unlike the Particle-in-Cell method [Dawson, 1983] which simply adds up the contribution of meta-particles, this method does a reconstruction of the distribution function $f$ in every time step for each species. This interpolation method combines meta-particles with different weights in such a way that particles with large weight do not drown out particles that represent small contributions to the phase space density. These core properties allow the use of a much larger range of macro factors and can thus represent a much larger dynamic range in phase space density. The reconstructed phase space density $f$ is used to calculate momenta of the distribution function such as the charge density $\rho$. The charge density $\rho$ is also used as input into a spectral solver that calculates the self-consistent electrostatic field which is used to update the particles for the next time-step. Afterlive (A Fourier-based Tool in the Electrostatic limit for the Rapid Low-noise Integration of the Vlasov Equation) is fully parallelized using MPI and writes output using parallel HDF5. The input to the simulation is read from a JSON description that sets the initial particle distributions as well as domain size and discretization constraints. The implementation presented here is intentionally limited to one spatial dimension and resolves one or three dimensions in velocity space. Additional spatial dimensions can be added in a straight forward way, but make runs computationally even more costly.Comment: Accepted for publication in Computer Physics Communication

PICPANTHER: A simple, concise implementation of the relativistic moment implicit Particle-in-Cell method

A three-dimensional, parallelized implementation of the electromagnetic relativistic moment implicit particle-in-cell method in Cartesian geometry (Noguchi et. al., 2007) is presented. Particular care was taken to keep the C++11 codebase simple, concise, and approachable. GMRES is used as a field solver and during the Newton-Krylov iteration of the particle pusher. Drifting Maxwellian problem setups are available while more complex simulations can be implemented easily. Several test runs are described and the code's numerical and computational performance is examined. Weak scaling on the SuperMUC system is discussed and found suitable for large-scale production runs.Comment: 29 pages, 8 figure

Of Trees and Genealogies: A Foucauldian Commentary on Franco Moretti

This paper discusses Franco Moretti's concept of "distant reading" in the light of Foucauldian genealogy. It confronts Moretti's evolutionary understanding of literary history — as represented in his adoption of the figure of the Darwinian tree — with Foucault's interpretation of Darwin's evolutionary theory. With reference to Foucault's transition from 'Darwinian' discourse analysis to 'Nietzschean' genealogy, the author argues that Moretti's conception of literary history could benefit from the genealogical practice of a 'meticulous' close reading in order to keep sight of hidden power relations behind literary production

Emission of Type II Radio Bursts - Single-Beam versus Two-Beam Scenario

Peer reviewe

Nonlinear Wave Interactions as Emission Process of Type II Radio Bursts

Peer reviewe

Particle Acceleration in Magnetic Reconnection with Ad hoc Pitch-angle Scattering

Particle acceleration during magnetic reconnection is a long-standing topic in space, solar and astrophysical plasmas. Recent 3D particle-in-cell simulations of magnetic reconnection show that particles can leave flux ropes due to 3D field-line chaos, allowing particles to access additional acceleration sites, gain more energy through Fermi acceleration, and develop a power-law energy distribution. This 3D effect does not exist in traditional 2D simulations, where particles are artificially confined to magnetic islands due to their restricted motions across field lines. Full 3D simulations, however, are prohibitively expensive for most studies. Here, we attempt to reproduce 3D results in 2D simulations by introducing ad hoc pitch-angle scattering to a small fraction of the particles. We show that scattered particles are able to transport out of 2D islands and achieve more efficient Fermi acceleration, leading to a significant increase of energetic particle flux. We also study how the scattering frequency influences the nonthermal particle spectra. This study helps achieve a complete picture of particle acceleration in magnetic reconnection