Collisionless shocks and discontinuities in electron-ion-positron plasma

NAISS 2023/6-257


NAISS Medium Storage

Principal Investigator:

Mark Eric Dieckmann


Linköpings universitet

Start Date:


End Date:


Primary Classification:

10303: Fusion, Plasma and Space Physics

Secondary Classification:

10301: Subatomic Physics

Tertiary Classification:

10105: Computational Mathematics



We will address several problems in astrophysical plasma and in laboratory plasma. Astrophysical and Space plasma is usually collisionless because its particle number density is low. It can be as low as a few tens of particles per cubed centimetre in the Solar wind near the Earth. The mean-free path of particles in this plasma is comparable to the distance Sun-Earth. The Earth's bow shock has, however, a thickness of just a few tens of kilometres. It is evident that this shock is not mediated by binary collisions between particles. Laboratory plasma is collisionless if it is hot and moderately dense like in the case of a plasma that is created when a solid target is ablated by a laser pulse with a ultra-high intensity. In such a plasma, the particle's kinetic energy is large compared to variations of its energy in the electric potential of neighboring particles; hence binary interactions are unimportant. We will pursue three subprojects: Oscillations of shocks. We let shocks run across a local perturbation, which leads to their spatial deformation and to a modulation of the ion density and magnetic field direction along the shock boundary. Once the shock leaves the perturbation interval, it relaxes. Either it starts oscillating around its equilibrium value until the oscillations damp out or it reaches a new final shape. We will study with two-dimensional PIC simulations such shock oscillations and deformations for a wide range of initial conditions. Magnetowave instabilities in the density ramps of expanding laser-generated blast shells. We will model expanding collisionless plasma and observe the waves that grow in this density ramp. Waves grow, because a thermal anisotropy develops in response to the loss of thermal energy of electrons to the expanding ions. We will study with one and two-dimensional particle-in-cell simulations the growth of such waves for a wide range of plasma conditions that are relevant for laser-generated plasma. Raman scattering couples a laser beam to an electron density wave and a backscattered beam of laser light. Raman scattering constitutes a major obstacle to inertial confinement fusion, where the deposition of laser energy raises the energy density of a plasma to a level that exceeds the one required for thermonuclear fusion. We will study with one- and two-dimensional particle-in-cell and Vlasov simulations properties of this instability. Performing a series of two-dimensional simulations with large spatial grids results in large data sets, that can reach terabyte scale. We request 15 TB of mass storate in order to keep the data from several simulations available for processing and analysis.