A new technique for measuring E region plasma density profiles in the equatorial electrojet using a bistatic coherent scatter radar has recently been tested [ Hysell and Chau, 2001 ]. The technique utilizes the Faraday rotation of the obliquely and coherently scattered signal. Plasma density versus altitude is inferred from the rate of Faraday rotation as a function of range and elevation angle. A narrow beamwidth is required to minimize returns from unwanted azimuths, but this can be achieved in a bistatic experiment using relatively small antenna arrays with widely spaced elements. We give a sample time sequence of daytime electron density profiles that were measured with the new technique at altitudes between 95 and 110 km. Scatter from pure two-stream waves makes it possible to measure both the bottomside and topside density profiles during the day. The importance of this new technique becomes evident when it is realized that only a few rocket flights have provided density profiles through these altitudes at the magnetic equator; the region has been inaccessible to any remote sensing technique until now.
Below is a diagram of the radar sites and the antenna patterns used.