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I i i i i i i i i

Continuous observations of the amplitude and spectrum of naturally occurring radiation in the band 2–40 kc/s have been made during the period June to December 1958 near Sydney, Australia. A large number of isolated noise bursts lasting for some hours were detected. The intensity ranged from 6 × l0−19 to 6×10−-17W m−2 (c/s)−1at 4·6 kc/s. Three main types of bursts were identified and classified on a basis of their spectra which usually extended from 3 to 5 kc/s, 4 to 8 kc/s and 2 to 30 kc/s, respectively. Major bursts, which were always of the latter two types, were clearly associated with strong auroral and magnetic activity and some showed a reproducible sequence of amplitude variation lasting about 36 hours. On three occasions, a detailed correspondence between the intensity of the noise and of simultaneously occurring red oxygen airglow was observed. Theories of the origin of the noise are discussed.

Low-Frequency Electromagnetic Radiation Associated with Magnetic Disturbances

Atmospheric radio noise data on 25 and 50 Mc/s at Enkoping, Sweden, and Thule, Greenland, have been analyzed for 10 polar-cap and auroral-zone absorption events occurring in the years 1958–1960 Results show that the measured noise power is radically depressed during such events At Enkoping, ‘maximum decrease’ on 25 and 50 Mc/s ranged from 10 to 36 db and from 6 to 38 db below normal, respectively The corresponding ranges at Thule were 5 to 24 and 6 to 14 db below normal Noise amplitude distribution curves are similar in shape for both ionospherically quiet and disturbed periods; on the average, the disturbed-period envelope is about 7 db below normal

Polar‐cap and auroral‐zone absorption effects on 2.5‐ and 5.0‐megacycles per second atmospheric radio noise

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=12029&context=rtd

A predictive model of the HF noise environment at satellite heights

The effect of variations in temperature and nitric oxide density on ion-clustering in the mesopause region during winter anomaly

A study was made to determine the feasibility of using artificial earth satellites to monitor thunderstorm activity. The nighttime noise-temperature measurements made with the earth-oriented vee antenna of the Radio Astronomy Explorer (RAE 1) satellite in the frequency range 0.2-9.2 MHz were correlated with reported surface thunderstorm activity. Analysis shows that the minimum nighttime HF noise level (in the absence of surface thunderstorms) at an altitude of 5850 km over the United States is fixed by man-made noise. When thunderstorms are active below the satellite, the noise level is increased by about 6-12 dB. The highest level is associated with the most intense storms. It is concluded that thunderstorm regions can be detected by an orbiting satellite using HF radio techniques, but ionospheric effects must be taken into account.

Radio detection of thunderstorm activity with an earth-orbiting satellite

Analysis of radio noise records from Kekaha, Hawaii, and Ohira, Japan, during 75 solar flares occurring during August, September, and October 1958 reveals a positive relationship between short-time noise power decreases and solar flares. The most significant noise fadeouts associated with flare eruptions occurred with the sun over one of the major noise centers contributing to the noise level at the measuring station. Maximum noise decrease of 18 db was observed on 5.0 Mc/s at Kekaha when the sun was over the East Indies noise center, just after sunset at the receiver.

John R. Herman

Papers

Polar‐cap and auroral‐zone absorption effects on 2.5‐ and 5.0‐megacycles per second atmospheric radio noise

Radio detection of thunderstorm activity with an earth-orbiting satellite

Solar‐flare effects on 2.5 and 5.0 Mc/s atmospheric radio noise