  The Weibel instability is investigated with PIC simulations of an initially
unmagnetized and spatially uniform electron plasma. This instability, which is
driven by the thermally anisotropic electron distribution, generates
electromagnetic waves with wave vectors perpendicular to the direction of the
higher temperature. Two simulations are performed: A 2D simulation, with a
simulation plane that includes the direction of higher temperature,
demonstrates that the wave spectrum is initially confined to one dimension. The
electric field components in the simulation plane generated by the instability
equalize at the end of the simulation through a secondary instability. A 1D PIC
simulation with a high resolution, where the simulation box is aligned with the
wave vectors of the growing waves, reveals details of the electron phase space
distribution and permits a comparison of the magnetic and electric fields when
the instability saturates. It is shown that the electrostatic field is driven
by the magnetic pressure gradient and that it and the magnetic field
redistribute the electrons in space.
