Measurements of the plasma line by incoherent scatter at Nancay and first morphological results

Results are presented for the measurement of the plasma line in an incoherent scatter spectrum obtained by a bistatic probe. Following a theoretical review of processes in the ionospheric plasma, a measurement technique is proposed which permits accurate determination of relevant parameters every 35 sec for a given altitude. These parameters are the line frequency as a measure of the electron density, the line width as a measure of the electron density gradient in most cases, and the line power as a function of the photoelectron flux. Simultaneous calculation of these parameters makes it possible to measure the sharp fluctuations in electron density and to estimate the shape of the photoelectron spectrum for energies below 5 eV.