Evidence of naturally occurring wave-wave interactions in the polar ionosphere and its relation to naturally enhanced ion acoustic lines

In this paper we offer the first study of seldom‐recorded naturally occurring wave‐wave interactions in the polar ionosphere, using the first such data set acquired with the EISCAT Svalbard Radar (ESR). The simultaneous and co‐located observations of enhancements in the ion and plasma lines can only be explained in terms of wave‐wave interactions taking place within the scattering volume. These measurements strengthen previous indications that Langmuir turbulence triggered by a low energy electron beam associated with the aurora is probably the source of many of the Naturally Enhanced Ion Acoustic Lines (NEIAL) observed with incoherent scatter radars over the last decade.