ASTROPHYSICS

Vlasiator is developed with a European Research Council Starting grant (2008-2013). It is a unique large-scale global space weather model, which can accurately describe plasmas to a degree that currently cannot be self-consistently described by the existing global space weather simulations. Due to the multi-dimensional approach in ion scales, Vlasiator’s computational challenges are immense requiring high performance computing techniques to allow massively parallel computations.

During this PRACE grant period, Vlasiator has seen a large set of technical improvements, allowing almost linear scaling up to 100,000 cores, and enabling more comprehensive analysis. Vlasiator offers in-depth studies of magnetospheric processes such as magnetic reconnection, and particle
 acceleration.

Normally in space physics, upstream solar wind phenomena cause downstream dynamical variations, while downstream phenomena have not been thought to cause upstream phenomena. As a surprise, the latest PRACE Tier-0 grant enabled runs showing that some
 phenomena downstream can lead to perturbations of the shape of the shock that encompasses the Earth’s magnetic domain. This discovery is confirmed by in-situ spacecraft observations and is the subject of an
 article submitted to a peer-reviewed journal.

Magnetic reconnection is one of the most important processes in plasmas, transforming magnetic energy to kinetic energy by accelerating particles. With the new runs, the Vlasiator team is able to, for the first time in the world, look at the reconnection process simultaneously in the entire Earth’s magnetic domain, and to witness dayside reconnection driving nightside reconnection. This reveals a rich playground of collective phenomena that cannot be interpreted by spacecraft observations only, nor with earlier simulation methods. These results have been presented in major international conferences, and will be submitted to a peer-reviewed journal in 2016.