Radio scattering in the lower ionosphere

Radio-scatterrng phenomena at the 80- to 90-km level observed in the frequency range 30 to 100 Mc indicate the presence of irregulartties of electron density with scales in the range from 20 to 60 meters (cornugation wavelengths from 120 to 360 meters). The irregularities are approximately isotroprc, and the scattered power is inversely proportional to about the sixth power of scale. The power law involved may vary somewhat with the state of the atmosphere. The fading of the radio waves is consistent with random motions of the irregularities with velocities of the order of 25 m/sec. Similar observations of the sporadic-E phenomena occurring at a height of about 110 km show that the scattered power rs inversely proportional to something like the eighteenth power of scale while the velocity of irregularities, if interpreted as random, is around 5 m/sec. (auth)