Satellite observation of discrete VLF line radiation within transmitter‐induced amplification bands

Abstract

Narrow‐band VLF signals with a frequency separation of 100–130 Hz have been detected by a receiver aboard the S3‐3 satellite. The observations were made at L = 2.9 at an altitude of 5700 km. Satellite nadir was 45°N and 151°E. The radiation has the same characteristics as those reported for ground‐based observations of magnetospheric lines resulting from the nonlinear amplification of power line radiation. As is seen in ground‐based observations, the lines are not exact harmonics of the power system frequency, nor are they spaced at exactly 2 or 3 times that frequency. The frequencies of the three dominant lines were typically 7364, 7494, and 7598 Hz. During the time period of these observations the transportable very low frequency (TVLF) transmitter was performing magnetospheric wave injection experiments from a site in Central Otago, New Zealand. The modulation was 0.5 Hz frequency shift keying between 7350 and 8780 Hz. The narrow‐band signals detected by the S3‐3 satellite were observed in the 250‐Hz band above the lower frequency. The narrow‐band magnetospheric lines were apparently observed because power line harmonic radiation was amplified to detectable levels by a nonlinear interaction involving the TVLF signal. The most likely sources of the power line radiation are the 50‐Hz power grids in Tasmania, southeastern Australia, or New Zealand.

ELF magnetospheric lines observed by DEMETER

“…They are observed during periods of moderate or intense magnetic storms. This is similar to observations performed by Koons et al (1978) with the S3-3 satellite or by Park (1977) with a ground-based experiment.…”

“…Park (1977) observed ground-based PLHR during a magnetic storm. However, direct observations by satellites are rather rare and shown in few papers (Koons et al, 1978;Bell et al, 1982;Tomizawa and Yoshino, 1985;Parrot, 1994;Rodger et al, 1995)…”

Magnetospheric line radiation observations at Halley, Antarctica

“…Evidence for the power line harmonic generation Satellite observations of MLR events have also reported on the occurrence and frequency spacing of MLR. One VLF spectrogram out of 115 (0.9%) recorded by the satellite S3-3 showed activity similar to MLR [Koons et al, 1978]. The VLF wave experiment on board ISEE 1 detected MLR in fiveof 90 orbits, leading the authors to suggest that there is a 1% probability of detecting MLR activity [Bell et al, 1982].…”

Physical mechanisms of man-made influences on the magnetosphere

“…Indirect effects were reported by FraserSmith (1981), Matthews and Yearby (1981), Bullough et al (1985) and Parrot (1990). Direct observations from satellites were given by Koons et al (1978), Park and Helliwell (1981), Bell et al (1982), and Parrot (1994). At VLF frequencies between 10 and 30 kHz, the ground-based transmitters are used for radio-navigation and communications.…”