MEASUREMENTS OF THE VLF SCATTERING PATTERN OF THE STRUCTURED PLASMA OF RED SPRITES

Analysis of a large number of VLF scattering events associated with sp rites results in an average scattering distribution having a strong fr ontal lobe, and also having strong large-angle scattering. This is con sistent with the scattering pattern produced by a theoretical model of the sprite as an array of interacting vertical plasma columns, indica ting that some part of the sprite is ''hard'' and contains complex str ucture (most likely the ''stalactites'' seen in optical sprites). Atte mpting to determine the scattering distribution due to sprites using a high threshold for event detection could result in observation of onl y the frontal lobe and the minima on either side of it, and not the sc attering at larger angles. This problem would be worsened by the use o f only amplitude, and not phase, monitoring to detect perturbations, a nd could lead experimenters to the conclusion that sprites are narrow- angle scatterers, with a smoothly varying diffuse structure.