This visualization represents Laser Wakefield acceleration, which is driven by an intense laser that propagates through 400 micrometers of plasma. This is a short laser pulse, which one can imagine as a compact ball of light that excites plasma waves during its travel. Some electrons can be lucky enough to "surf" a plasma wave. Much like the real surfers, it is important for electrons to have some initial velocity to be able to "catch" the wave. Once they start surfing, they can reach very high energies in a short propagation distance.
Simulation by M. Vranic using the PIC code OSIRIS@GoLP, visualization by ELI Beamlines
SIDE - slice
FRONT - integration