Study of nonlinear ion- and electron-acoustic waves in multi-component space plasmas

G S Lakhina,A P Kakad,R Bharuthram,F Verheest,S V Singh

doi:10.5194/npg-15-903-2008

Abstract

Abstract. Large amplitude ion-acoustic and electron-acoustic waves in an unmagnetized multi-component plasma system consisting of cold background electrons and ions, a hot electron beam and a hot ion beam are studied using Sagdeev pseudo-potential technique. Three types of solitary waves, namely, slow ion-acoustic, ion-acoustic and electron-acoustic solitons are found provided the Mach numbers exceed the critical values. The slow ion-acoustic solitons have the smallest critical Mach numbers, whereas the electron-acoustic solitons have the largest critical Mach numbers. For the plasma parameters considered here, both type of ion-acoustic solitons have positive potential whereas the electron-acoustic solitons can have either positive or negative potential depending on the fractional number density of the cold electrons relative to that of the ions (or total electrons) number density. For a fixed Mach number, increases in the beam speeds of either hot electrons or hot ions can lead to reduction in the amplitudes of the ion-and electron-acoustic solitons. However, the presence of hot electron and hot ion beams have no effect on the amplitudes of slow ion-acoustic modes. Possible application of this model to the electrostatic solitary waves (ESWs) observed in the plasma sheet boundary layer is discussed.

Highlights

The boundary layers of the Earth’s magnetosphere can support a variety of electrostatic and electromagnetic wave modes, e.g., Alfven modes, whistler waves, broadband electrostatic noise (BEN), etc
Analysis of the high time resolution of the plasma wave data from GEOTAIL have shown that BEN in the plasma sheet boundary layer consists of short electrostatic solitary waves (ESWs) whose Fourier spectrum give rises to the broadband nature of the noise (Matsumoto et al, 1994)
It is interesting to note that the electrostatic solitary structures are observed in the electric field parallel to the background magnetic field, are usually bipolar or tripolar, and their amplitudes are typically a few mV/m in the plasma sheet boundary layer, but they can be as large as 200 mV/m at polar altitudes (Cattell et al, 1999)

Summary

Introduction

The boundary layers of the Earth’s magnetosphere can support a variety of electrostatic and electromagnetic wave modes, e.g., Alfven modes, whistler waves, broadband electrostatic noise (BEN), etc.

Results

Conclusion