VERY LOW FREQUENCY RADIO WAVE PROPAGATION AT HIGH-LATITUDES

• Main Authors: Riedler,Willi, Egeland,Alv
• Other Authors: KIRUNA GEOPHYSICAL OBSERVATORY (SWEDEN)
• Format: Text
• Language: English
• Published: 1963
• Subjects: (*IONOSPHERIC PROPAGATION; VERY LOW FREQUENCY); RADIO WAVES; VERY LOW FREQUENCY; INTENSITY; DIURNAL VARIATIONS; PERIODIC VARIATIONS; GEOMAGNETISM; SUNSPOTS; Kiruna
• Online Access: http://www.dtic.mil/docs/citations/AD0415186; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0415186

Diurnl, seasonal and yearly variations of the normal 16 kc signal strength from the Rugby (GBR) transmitter were studied on the basis of data accumulated during approximately five years of continuous recording (September 1958 to May 1963) at Kiruna Geophysical Observatory. The observed day-night variation of the 16 kc signal strength is discussed in terms of the mode theory of prop agation, in a first-order approximation. For the case when the night-time signal level is lower than the daytime level (as for the years 1958 to 1961), an increase of apparent reflection heights from 70 km at day to 80-85 km at night can explain the observation. An increase in reflection heights of say 5 to 10 km both during night and day, may explain the observations obtained during the more quiet ionospheric conditions in 1961 to 1963; namely that the night-time signal strength was of greater intensity than that during the daytime. The reception of 16 kc Rugby transmissions at Uppsala supports this conclusion. The marked decrease in ionospheric absorption for the periods when the night-time level of the 16 kc signal strength exceeded the day-time level, can be understood if the region, where the main part of the ionospheric absorption, as well as the reflection of very low frequency waves takes place, was some kilometers higher than during the remainder of the observation period. (Author)