UARS measures the flux of energetic particles from space using the Particle Environment Monitor, PEM. These high energy particles cause ozone depletion at high altitudes by producing nitrogen and hydrogen radicals. Note: Energetic particle flux over the arctic as measured by PEM on 11-9-91. Animator: Horace Mitchell (NASA/GSFC). Scientist: Mark Schoeberl (NASA/GSFC). Platforms/Sensors/Data Sets: UARS/PEM.