The temporal evolution of 3‐m striations in the modified ionosphere

Experiments were performed at Arecibo, Puerto Rico, to investigate the evolution times of 3-m field-aligned Striations produced in the ionosphere by powerful high-frequency (HF) radio waves. The results of this investigation are now summarized. First, the striations' rise times are dependent on the HF electric field. The E region data suggest that this dependence is nonlinear. Second, the threshold value of the HF electric field required to produce detectable Striations was experimentally determined. At threshold the component of the HF electric field perpendicular to the geomagnetic field is calculated to be 0.09 V/m in the F region and 0.37 V/m in the E region. Third, both the E and the F region data verify theoretical predictions that the Striations' decay times are directly proportional to the electron diffusion across B. Finally, a one-to-one correspondence between the growth of the 3-m Striations and the decline of the HF-enhanced plasma line during overshoot is sometimes observed.