Generation of large-scale field-aligned irregularities in ionospheric modification experiments


  • Bruce L. Cragin,

  • J. A. Fejer


The threshold of the purely growing mode of stimulated Brillouin scattering is exceeded in ionospheric modification experiments for horizontal wave-lengths longer than about half a km. The “beat wavelength” along the field lines is a few km long and increases with decreasing height. The irregularities are therefore not purely field aligned initially although diffusion across the field lines could, over longer periods of time, produce purely field-aligned irregularities which persist after the heating transmitter is switched off.