Abnormal Ionization in the E Region of the Ionosphere

Abstract

Records of the field strength of 10-megacycle signals have been made at a distance of 30 kilometers from the transmitter. "Bursts" of received energy, of a few minutes' duration, were noted at times when no reflection from the F layer was present. When the density of ionization in the F layer was above the critical value for this frequency, occasional short periods of strong absorption at a low level have greatly reduced the strength of the reflected signal. Both of these phenomena are apparently due to small volumes of dense ionization in the E region, and they are consistent with a theory that such local ionization is caused by the transit of a single large meteor. Examination of astronomical data on the number and size of meteors shows that this is a possible explanation of the abnormally intense ionization frequently observed in the E layer. The same recently accessible data indicate that the constant meteoric bombardment of the atmosphere can maintain a continuous background level of ionization in the E region of about the magnitude which is observed during the night.