PICsar: A 2.5D axisymmetric, relativistic, electromagnetic, Particle in Cell code with a radiation absorbing boundary

•Presented a new 2.5D axisymmetric Particle in Cell code, PICsar.•PICsar is designed for efficiently simulating the pulsar magnetosphere.•PICsar is 10,000 times faster than a 3D Cartesian code for axisymmetric sims.•Tested PICsar using a specially designed series of tests.•Simulated magnetic monopole geometry to 1% accuracy.

We present PICsar – a new Particle in Cell code geared towards efficiently simulating the magnetosphere of the aligned rotator. PICsar is a special relativistic, electromagnetic, charge conservative code that can be used to simulate arbitrary electromagnetics problems in axisymmetry. It features stretchable body-fitted coordinates that follow the surface of a sphere, simplifying the application of boundary conditions in the case of the aligned rotator; a radiation absorbing outer boundary, which allows a steady state to be set up dynamically and maintained indefinitely from transient initial conditions; and algorithms for injection of charged particles into the simulation domain. The code is parallelized using MPI and scales well to a large number of processors. We discuss the numerical methods used in PICsar and present tests of the code. In particular, we show that PICsar can accurately and efficiently simulate the magnetosphere of the aligned monopole rotator in the force-free limit. We present simulations of the aligned dipole rotator in a forthcoming paper.