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Spreading of waves emitted from an ELF/VLF source in the magnetosphere
Author(s) -
Kelly Francis J.,
Baker Dennis J.,
Chayt Gerald A.
Publication year - 1976
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs011i002p00093
Subject(s) - ionosphere , magnetosphere , physics , geophysics , point source , ranging , radio wave , ray tracing (physics) , geology , remote sensing , computational physics , geodesy , optics , magnetic field , quantum mechanics
Electromagnetic waves from an ELF/VLF source in the magnetosphere may be propagated through the ionosphere to receiving antennas on the earth's surface. Among many factors important in estimating the received signal strength is the geometric spreading factor, d Ω' dA E , measuring the area, dA E , of the earth's surface intercepting the power radiated into the solid angle, d Ω from the source. The spreading factor has been isolated and accurately estimated by a ray‐tracing computer program. Calculations have been performed for transmissions at 3 and 10 kHz and for three different ionospheric models using source altitudes ranging between 300 and 8000 km for some representative receiver point locations. Spreading factors were calculated both for direct and multiple hop waves in the earth‐ionosphere waveguide. For low source altitudes (below about 2200 km) the coverage patterns of spreading‐factor versus the receiver's geographic position showed well‐defined peaks, indicating locally high radio fields. For higher altitudes the coverage patterns were broader but showed weaker maximum field strengths. A comparison was made with a simply estimated factor employed by Smith and Rorden, and quantitative and qualitative differences are noted.