Nonlinear electron acoustic structures generated on the high-potential side of a double layer

Abstract

Abstract. High-time resolution measurements of the electron distribution function performed in the auroral upward current region reveals a large asymmetry between the lowand high-potential sides of a double-layer. The latter side is characterized by a large enhancement of a locally trapped electron population which corresponds to a significant part (∼up to 30%) of the total electron density. As compared to the background hot electron population, this trapped component has a very cold temperature in the direction parallel to the static magnetic field. Accordingly, the differential drift between the trapped and background hot electron populations generates high frequency electron acoustic waves in a direction quasi-parallel to the magnetic field. The density of the trapped electron population can be deduced from the frequency where the electron acoustic spectrum maximizes. In the auroral midcavity region, the electron acoustic waves may be modulated by an additional turbulence generated in the ion acoustic range thanks to the presence of a pre-accelerated ion beam located on the high-potential side of the double layer. Electron holes characterized by bipolar pulses in the electric field are sometimes detected in correlation with these electron acoustic wave packets.

Nonlinear ion-acoustic (IA) waves driven in a cylindrically symmetric flow

“…It offers an alternative to explain inverted-V structures in beam-precipitating regions (Pottelette & Berthomier 2009), as to be contributed in a companion paper. This is based on the considerations as follows.…”

Electron acoustic double layers in a plasma with a q-nonextensive electron velocity distribution

“…Our investigation may be of wide relevance to astronomers and space scientists working on interstellar and space plasmas. It is worth to note that some theoretical work focused on nonlinear electron-acoustic waves (Singh and Lakhina 2004;Cattaert et al 2005;Verheest et al 2007;Gill et al 2007;Lakhina et al 2008aLakhina et al , 2008bPottelette and Berthomier 2009;Pakzad and Tribeche 2010;Younsi and Tribeche 2010). The manuscript is organized as follows: In the next section, we present the basic equations of our theoretical model and derive the pseudo-potential associated to localized electron-acoustic double-layers.…”

Small-scale filamentary structures recorded in the auroral regions connected to the plasma sheet boundary layer

“…Measuring electron number density from an electrostatic analyzer is difficult, especially at low energies, where spacecraft photoelectrons often dominate the electron flux [Ergun et al, 1998b;Strangeway et al, 1998]. On the other hand, electron acoustic waves are an ideal indicator of the presence of a cold electron component Pottelette and Berthomier, 2009]. Here we take the advantage that when the hot to cold temperature ratio becomes larger than 10, the electron acoustic mode becomes more excited than the Langmuir mode and can be considered as the principal high-frequency mode of the plasma [Tokar and Gary, 1984;Gary and Tokar, 1985].…”