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Cutaway drawing of two radiation belts around Earth: the inner belt (red) dominated by protons and the outer one (blue) by electrons. Image Credit: NASA Image Credit: NASA The inner Van Allen Belt extends typically from an altitude of 0.2 to 2 Earth radii ( L values of 1.2 to 3) or 1,000 km (620 mi) to 12,000 km (7,500 mi) above the Earth.
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency [1] range from around 20 kHz to around 300 GHz.
Paramagnetic materials are attracted to magnetic fields, hence have a relative magnetic permeability greater than one (or, equivalently, a positive magnetic susceptibility). The magnetic moment induced by the applied field is linear in the field strength, and it is rather weak. It typically requires a sensitive analytical balance to detect the ...
The radio window is the region of the radio spectrum that penetrate the Earth's atmosphere. Typically, the lower limit of the radio window's range has a value of about 10 MHz (λ ≈ 30 m); the best upper limit achievable from optimal terrestrial observation sites is equal to approximately 1 THz (λ ≈ 0.3 mm). [1] [2]
A Type I civilization is usually defined as one that can harness all the energy that reaches its home planet from its parent star (for Earth, this value is about 2 × 10 17 watts), which is about four orders of magnitude higher than the amount currently achieved on Earth, with an energy consumption of ≈2 × 10 13 watts by 2020.
When the refractive index of the medium is greater than one, ELF waves propagate slower than the speed of light in vacuum. As used in military applications, the wavelength is 299,792 km (186,282 mi) per second divided by 50–85 Hz, which equals around 3,500–6,000 km (2,200–3,700 mi) long.
Rayleigh scattering of sunlight in Earth's atmosphere causes diffuse sky radiation, which is the reason for the blue color of the daytime and twilight sky, as well as the yellowish to reddish hue of the low Sun. Sunlight is also subject to Raman scattering, which changes the rotational state of the molecules and gives rise to polarization ...
A frequency vs. time plot (spectrogram) showing several whistler signals amidst a background of sferics as received at Palmer Station, Antarctica on August 24, 2005.A radio atmospheric signal or sferic (sometimes also spelled "spheric") is a broadband electromagnetic impulse that occurs as a result of natural atmospheric lightning discharges.