Magnetic reconnection is the fundamental process which allows magnetized plasmas to convert the energy stored in the field lines into kinetic energy of the plasma. It plays an important role in the dynamics of space and laboratory plasmas. In the magnetopause it allows particles from the solar wind to enter the magnetosphere and it is believed to be the main source of energy for solar flares and coronal mass ejections.

Previous investigations showed that the minimal model to adequately describe collisionless reconnection is Hall-MHD. While it is known that the Hall term is vital for reconnection for reconnection, it vanishes at the neutral X--line where the magnetic field strength is exactly zero. Here, only the electron bulk inertia and the non gyrotropic part of the electron pressure tensor can yield a contribution at the X--line.

In this presentation, I will report Vlasv simulations of collisionless reconnection. In contrast to Particle--In--Cell (PIC) codes, Vlasov codes discretise the complete distribution functions of electrons and ions on a grid in phase space. Because numerical noise is completely absent from the Vlasov-approach, allows more detailed investigations ofthe distribution functions, and the origin of the non-gyrotropic part of the electron pressure tensor.