HF radar observations of decaying artificial field‐aligned irregularities

Abstract

Bistatic HF radar scatter from magnetic field‐aligned irregularities created by the Sura heater near Nizhny Novgorod, Russia, has been detected and analyzed at the UTR 2 decametric radio telescope near Kharkov, Ukraine. The decay phase of the irregularities exhibits two decay time constants in general. The shorter time constant, which is only sometimes seen, is consistent with classical diffusive dissipation theory for small‐scale, field‐aligned waves. The longer time constant, which is almost always present, is much too long to be accounted for by diffusion. It is more likely associated with the decay of large‐ and intermediate‐scale plasma turbulence. Three‐wave nonlinear interaction with turbulent modes is shown to be capable of generating the field‐aligned irregularities.