MHD-AEPIC simulation of a geomagnetic storm. The 2D cuts display a part of the much larger 3D domain. Colors show the X component of the velocity and the white lines are traces of the magnetic field in the meridional plane. The black lines in the two snapshots, separated by 159 minutes of simulation time, indicate the edges of the active PIC regions. As the tail evolves, the active PIC region is continuously adapted to cover the reconnection sites of interest.