On the nature of the electrojet irregularities responsible for daytime VHF scintillations

The nature of electrojet irregularities responsible for daytime VHF scintillations at 41 and 140 MHz observed at Huancayo, Peru, has been examined by conducting a study of simultaneous scintillation measurements, ionograms, and 50-MHz oblique radar backscatter. It is found that the times of onset and decay of VHF scintillations correspond closely with the times of onset and decay of type 2 irregularities identified by the radar as well as Esq echoes oil ionograms, indicating thereby that type 2 irregularities cover the scale size range of at least 1 km to a few meters. By assuming a three-dimensional irregularity power spectrum of spectral index 4 and an outer scale dimension of 2 km the range of daytime scintillations at 41 MHz is shown to be consistent with irregularity amplitudes of approximately 5–15% for an ambient ionization density of 1011 m−3.