Enhanced ion acoustic fluctuations and ion outflows

F. R. E. Forme, D. Fontaine
1999 Annales Geophysicae  
A number of observations showing enhanced ion acoustic echoes observed by means of incoherent scatter radars have been reported in the literature. The received power is extremely enhanced by up to 1 or 2 orders of magnitude above usual values, and it is mostly contained in one of the two ion acoustic lines. This spectral asymmetry and the intensity of the received signal cannot be resolved by the standard analysis procedure and often causes its failure. As a result, and in spite of a very clear
more » ... ite of a very clear spectral signature, the analysis is unable to ®t the plasma parameters inside the regions of ion acoustic turbulence. We present European Incoherent Scatter radar (EISCAT) observations of large ion out¯ows associated with the simultaneous occurrence of enhanced ion acoustic echoes. The ion¯uxes can reach 10 14 m A2 s A1 at 800 km altitude. From the very clear spectral signatures of these echoes, a method is presented to extract estimates of the electron temperature and the ion drift within the turbulent regions. It is shown that the electron gas is strongly heated up to 11 000 K. Also electron temperature gradients of about 0.02 K/m exist. Finally, the estimates of the electron temperature and of the ion drift are used to study the possible implications for the plasma transport inside turbulent regions. It is shown that strong electron temperature gradients cause enhancement of the ambipolar electric ®eld and can account for the observed ion out¯ows.
doi:10.1007/s00585-999-0182-6 fatcat:ed4hdxk3xvdfphwfdcilaoo4rm