Measurement of the phase velocity of VLF propagation in the earth-ionosphere waveguide

Abstract

For short periods of time during June and July of 1963 t he U.S. Navy t rans mitters located at Jim Creek, Wash. (NPG), and Balboa, Panama (NBA), simulta neo usly t ransmitted a frequency stabilized signal of 18 kc/s . The phase and relative amplit ud c of these s ignals were monitored at Boulder, Colo.; College, Alaska; lVlau i, H awaii ; and Tu cum{m, Argentin a. A sc mi e mpirical method by which the mean r elative phase velocity can be calculated from t he measurements of ph ase made at t hese four l"rcording s ites is demonstrated. The va lues of t he mean r elative phase velocity a t 18 kc/s w hi ch are obtain ed for daytime and nighttime propagation cond itions are resp ectively, (Vp / c)

Results Concerning the Sunrise Effect of VLF Signals Propagated Over Long Paths

“…the sunlit and non-sunlit ·portion oi the propagation path respectively, t/11 and t/12 for the phases of the e~ci tation factors, and t/121 for the phase of the conversiOn factor at the night-day transition. Since the phase velocity is only slightly below the speed of light co, (1) and (2) give for the phase difference ll¥' at the receiving site: were given by Wait (l962b); they are in good agreement with experimental results (Wait, 1961;Steele and Chilton, 1964). The b..qJ-curves plotted in figure 5 were calculated with these values for ionospheric reflection heights of hE= 85 km and of hE= 90 km.…”

New Measurements of Phase Velocity at VLF

“…This value, within the precision of the measurement, agrees with a previous experimental result, using a different method, obtained by Steele and Chilton [1964] where they interpret their measurement as applying to mode I. The value is also in agreement with a theoretical mode 1 value obtained by Wait and Spies [1964] for an exponential model of the ionosphere with a reference height of about 80 km (case with no earth magnetic field).…”

Observations on the Propagation Constant of the EarthIonosphere Waveguide in the Frequency Band 8 c/s to 16 kc/s

“…The first experiments of this type are those of Taylor and Lange [1958], who deduced attenuation rates in the VLF band, and Jean, Taylor, and Wait [1960], who obtained values for the phase velocity in this band. Absolute determinations of phase velocity have also been made in the upper VLF band from observations on radio transmitters [Wait, 1961b;Steele and Chilton, 1964;Burgess, 1966].…”