THE DISPERSION RELATIONS AND INSTABILITY THRESHOLDS OF OBLIQUE PLASMA MODES IN THE PRESENCE OF AN ION BEAM

An ion beam can destabilize Alfven/ion-cyclotron waves and magnetosonic/whistler waves if the beam speed is sufficiently large. Numerical solutions of the hot-plasma dispersion relation have previously shown that theminimum beam speed required to excite such instabilities is significantly smaller fo...

Full description

Saved in:
Bibliographic Details
Published in:The Astrophysical journal 2013-02, Vol.764 (1), p.1-12
Main Authors: VERSCHAREN, DANIEL, Chandran, Benjamin D G
Format: Article
Language:English
Subjects:
ALPHA PARTICLES
APPROXIMATIONS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BEAMS
Beams (radiation)
COLD PLASMA
Conservation
CYCLOTRON RESONANCE
CYCLOTRONS
DISPERSION RELATIONS
Dispersions
Focusing
HOT PLASMA
Instability
Ion beams
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
NUMERICAL SOLUTION
PARTICLES
PLASMA INSTABILITY
POLARIZATION
QUASILINEAR PROBLEMS
SOLAR WIND
Stability
SUN
Thresholds
TURBULENCE
WHISTLERS
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:An ion beam can destabilize Alfven/ion-cyclotron waves and magnetosonic/whistler waves if the beam speed is sufficiently large. Numerical solutions of the hot-plasma dispersion relation have previously shown that theminimum beam speed required to excite such instabilities is significantly smaller for oblique modes with k x B sub(0) [not =] 0 than for parallel-propagating modes with k x B sub(0) = 0, where k is the wavevector and B sub(0) is the background magnetic field. In this paper, we explain this difference within the framework of quasilinear theory, focusing on low- beta plasmas. We begin by deriving, in the cold-plasma approximation, the dispersion relation and polarization properties of both oblique and parallel-propagating waves in the presence of an ion beam. We then show how the instability thresholds of the different wave branches can be deduced from the wave-particle resonance condition, the conservation of particle energy in the wave frame, the sign (positive or negative) of the wave energy, and the wave polarization. We also provide a graphical description of the different conditions under which Landau resonance and cyclotron resonance destabilize Alfven/ion-cyclotron waves in the presence of an ion beam. We draw upon our results to discuss the types of instabilities that may limit the differential flow of alpha particles in the solar wind.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/764/1/88