APPLICATION OF THE CODED LONG-PULSE TECHNIQUE TO PLASMA LINE STUDIES OF THE IONOSPHERE

Recently, the coded long-pulse radar technique was tested at Arecibo O bservatory, Puerto Rico using photoelectron-enhanced plasma lines in t he daytime ionosphere. The technique immediately proved to be a powerf ul diagnostic tool for studying natural ionospheric phenomena. Our ini tial observations indicate that extremely accurate measurements of abs olute electron density (0.01 to 0.03% error bars) can be achieved with an altitude resolution of 150 m and a temporal resolution of similar to 2 s. In addition, the technique provides information about electron density structure within a 150-m altitude cell and yields parameters from which the energy spectrum of suprathermal electrons (greater than or equal to 5 eV) can be deduced. Our earliest measurements are used to illustrate applications of the coded long-pulse technique to severa l aeronomic/ionospheric areas of current interest. These include studi es of neutral wave motions in the lower thermosphere, measurements of ion composition in the F-1 region/upper ionosphere, and investigations of electron-gas thermal balance and photoelectron energy loss process es. The technique can be utilized to examine irregularity formation in the F region, probe electron acceleration processes in ionospheric mo dification experiments, verify the magnetic field dependence of Langmu ir wave damping, and more generally test higher order corrections sugg ested for the Langmuir dispersion relation. It is anticipated that the latter tests will facilitate measurements of ionospheric currents.