The Earth as a radio source: Terrestrial kilometric radiation
Abstract
Radio wave experiments on the Imp 6 and 8 satellites have shown that the earth emits very intense electromagnetic radiation in the frequency range of about 50-500 kHz. At peak intensity the total power emitted in this frequency range is about 109 W. The earth is therefore a very intense planetary radio source, with a total power output comparable to the decametric radio emission from Jupiter. We refer to this radio emission from the earth as terrestrial kilometric radiation. Terrestrial kilometric radiation appears to originate from low altitudes (less than 3.0 RE) in the auroral region. The intensity of the noise has a pronounced dependence on both the local time and the magnetic latitude of the observing point. At large radial distances the radiation is primarily observed on the poleward side of two cone-shaped surfaces that are centered on the earth and symmetrically located with respect to the northern and southern auroral zones. The magnetic latitude of the cone-shaped boundaries varies from greater than 50° in the local morning to near the magnetic equator in the local evening. Poleward of these boundaries the noise occurs in sporadic ‘storms’ lasting from ½ hour to several hours. Comparisons with auroral photographs obtained from the low-altitude polar-orbiting Dapp satellite show that the terrestrial kilometric radiation is closely correlated with the occurrence of discrete auroral arcs, which occur in the local evening region of the auroral zone. This association indicates that the kilometric radiation is probably generated by intense ‘inverted V’ electron precipitation bands, which cause the discrete auroral arcs. Possible mechanisms that can explain the generation and propagation of the terrestrial kilometric radiation are discussed.
- Publication:
-
Journal of Geophysical Research
- Pub Date:
- October 1974
- DOI:
- 10.1029/JA079i028p04227
- Bibcode:
- 1974JGR....79.4227G
- Keywords:
-
- Earth (Planet);
- Low Frequencies;
- Radio Emission;
- Satellite Observation;
- Terrestrial Radiation;
- Explorer Satellites;
- Geomagnetism;
- Long Wave Radiation;
- Power Spectra;
- Radiant Flux Density;
- Particles and Fields-Ionosphere: Auroral zone magnetic effects;
- Particles and Fields-Magnetosphere: General or miscellaneous;
- Solar Physics;
- Astrophysics;
- and Astronomy: Radio astronomy