Red sprites: Lightning as a fractal antenna

A new and improved model of red sprites is presented. Emphasis is placed in accounting for the puzzling observation of the spatial structure in the red sprite's optical emissions. The model relies upon a horizontal fractal lightning discharge, which generates the EMPs that excites the optical emissions in the lower ionosphere. It is shown that the fractal model may account for the observed sprite's spatially structured optical pattern, while reducing the typical charge threshold to approximately 100 C.