Ionospheric Small-Scale Structures and Turbulence Observations: A review

Measurements of the European incoherent scatter facility (EISCAT) occasionally indicate the presence for brief periods of ionospheric small-scale structures and turbulence at scales smaller than the typical space and time resolution of the radar. Such events violate the assumption of space and time uniformity used in the analysis of the received signal. This results in an erroneous estimate of the derived ionospheric parameters, or even in the failure of the analysis when the measured spectrum departs too much from its usual shape. We review recently published observations from EISCAT data of two types of such phenomena, namely the small-scale auroral structures of intense flow bursts, and the ion-acoustic turbulence. The large differences in their spectral signature and origin illustrate both the variety of the small-scale phenomena occuring in the ionosphere, and the capability of the incoherent scattering technique to detect them and to infer original informations on the mechanisms responsible for them.