Artificially produced field-aligned short-scale striations
Gordon, William E.
Master of Science
HF-radiowaves propagating in the ordinary mode and incident on an overdense ionosphere ( fHF < foF2 ) are known to excite parametric instabilities. Recent experiments showed that under the same conditions short-scale field-aligned striations are formed. The question concerning the interrelation of these two effects is not yet settled. An experiment was performed at the Arecibo Observatory during June 1977 with a 5 MHz radar installed on Guadeloupe island. The Guadeloupe radar had a line of sight perpendicular to the magnetic field lines in the F-region above Arecibo. The 5 MHz radar backscatter measurements from the region where these artificially produced field-aligned striations (AFAS) occur are used to get some insight into the geometry and the temporal behavior of AFAS. The energy density of the HF-field required to produce AFAS is estimated from the experimental data. Plasma-line data on the parametric instability obtained by the 43 MHz incoherent backscatter from the Arecibo Observatory is compared with the Guadeloupe 5 MHz radar data. Several mechanisms which were proposed to produce AFAS are discussed in the light of present and past experimental results.