Incoherent Scatter Radar - Spectral Signal Model and Ionospheric Applications

Abstract

Doppler radars find a widespread use in the estimation of the velocity of discrete hard-targets as described elsewhere in this volume. In case of soft-targets—collections of vast numbers of weakly scattering elements filling the radar beam—the emphasis typically shifts to collecting the statistics of random motions of the scattering elements—i.e., Doppler spectral estimation — from which thermal or turbulent state of the target can be inferred, as appropriate. For instance, in case of a plasma in thermal equilibrium, e.g., the quiescent ionosphere,a Doppler radar of sufficient power-aperture-product can detect, in addition to the plasma drift velocities, the densities, temperatures, and even current densities of charged particle populations of the probed plasma — such Doppler radars used in ionospheric research are known as incoherent scatter radars (ISR). In this chapter we will provide a simplified description of ISR spectral theories (e.g., Kudeki&Milla, 2011) and also discuss magnetoionic propagation effects pertinent to ionospheric applications of ISR’s at low latitudes. A second chapter in this volume focusing on in-beam imaging of soft-targets by Hysell & Chau (2012) is pertinent to non-equilibrium plasmas and complements the topics covered in this article.