Modeling the relaxation of red sprite plasma

Red sprites consist of multiple ionised columns extending above a thunderst orm from similar to 30 km to similar to 90 km. Electron densities in these columns are very much larger than the ambient background, perhaps fives ord ers of magnitude at 70 km. These highly ionized structures cause observable perturbations in subionospheric VLF transmissions known as "VLF Sprites". Three models of initial sprite electron density are considered, and using a realistic ionization relaxation model the time dependence of electron dens ity is derived. A 3-D Born propagation code of is used to compute the time profile of a VLF sprite. Two profiles show good agreement with the time sig nature experimentally observed, in that scattered amplitude and phase decre ase logarithmically with time. These simulations provide insight into the n ature and structure of sprite columns, and indicate an additional constrain t which should be applied to red sprite creation models.