Naturally Enhanced Ion-Acoustic Lines and Solitary Waves

Ekeberg, J.1, Stasiewicz, K.2, Eliasson, L.1 and Leyser, T. B.2

1 Swedish Institute of Space Physics, Kiruna, Sweden
2 Swedish Institute of Space Physics, Uppsala, Sweden

Since the identification of naturally enhanced ion-acoustic lines in incoherent radar spectra, there have been several suggestions of generation mechanisms. These generation mechanisms include current-driven instabilities, ion-ion two-stream instabilities and parametric decay of Langmuir waves. In spectra from the EISCAT Svalbard Radar (ESR), naturally enhanced ion-acoustic lines are often seen around local noon. Using ESR spectra and a two-fluid plasma description, we have investigated the possibility that these lines are caused by solitary waves.