A plasma is born.Creating a spark in the gap between two electrodes (top and bottom) generates an "ionization front" (colors indicate light intensity). Using laser-induced fluorescence, rather than this intrinsic light, researchers measured the precise changes in the electric field as the plasma formed. Image Credit: E. Wagenaars/Eindhoven Univ. of Tech.
A spark flying between a metal doorknob and your hand is an intricate chain of electrical events. Atoms are pulled apart into electrons and ions, and currents flow through the air. Researchers now report the first direct measurements of the sharply changing electric fields that pave the way for a visible flash in a precisely controlled laboratory arc. Their results provide concrete detail in an area where theoretical modeling remains scanty, and may offer a way to study electrical discharges in settings ranging from plasma televisions to lightning strikes.