On the determination of temperature and ionic composition by electron backscattering from the ionosphere and magnetosphere

Observations of the scattering of electromagnetic waves from thermal fluctuations in the electron density of the ionosphere and magnetosphere were previously used to investigate ion and electron temperatures and the electron density. This work was based on the assumptions that the only ions present were 0+, and that kD = 4 pi D/ LAMBDA /sub T/<< 1 ( lambda /sub T/ is the transmitted wavelength, and D is the Debye length). These conditions usually apply at F-region heights. The interpretation of such scattering is extended to conditions likely to apply above the F region, where increasing percentages of He+ and H/sup +/ are expected to occur, and where kD may not be very small. Detailed curves are presented for mixtures of 0/sup +/ and He+. It appears that, with a sufficiently powerful radar operating at a sufficiently low frequency, scatter observations alone can usually be used to determine the relative concentrations of O+ and He+ (and/or H+), as well as the electron and ion temperatures and the electron density. When information on one or more of these ionospheric properties is available from another source, simpler scatter observations can be used to complete the set. A simple transformation is given thatmore » accurately corrects the interpretation for values of kD up to unity.« less