Instability of finite amplitude circularly polarized Alfven waves

Journal Article · Sun Jan 15 04:00:00 EST 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/155829· OSTI ID:5188098

Goldstein, M L

A circularly polarized, large-amplitude Alfven wave in a plasma with finite plasma ..beta.. is shown to be unstable. The wave decays by coupling to random density and magnetic fluctuations in the ambient medium. Daughter waves are produced at the sidebands which are at the first harmonic of the Alfven wave frequency and wavenumber. This is a four-wave coupling in which the initial Alfven wave excites forward-propagating density and magnetic waves as well as a backward-propagating magnetic wave. In general, the driven waves are not normal modes of the plasma, although in the limit of ..beta -->..0 the ''decay'' instability is recovered in which the density wave is ion-acoustic and one of the magnetic waves is a backward-propagating Alfven wave. For parameters more typical of the solar corona and solar wind, large decay rates are found for 0.1 < or =..beta..< or =1 and 0.1< or =eta< or =0.9, where eta is the ratio of magnetic energy density of the initial Alfven wave to that of the background magnetic field. The possible role played by this instability in several astrophysical situations is briefly considered.

• Research Organization: NASA/Goddard Space Flight Center, Laboratory for Extraterrestrial Physics, Greenbelt, Maryland
• OSTI ID: 5188098
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 219:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics &amp; Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALFVEN WAVES
DECAY INSTABILITY
FLUID MECHANICS
HIGH-BETA PLASMA
HYDRODYNAMICS
HYDROMAGNETIC WAVES
INSTABILITY
ION ACOUSTIC WAVES
ION WAVES
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MECHANICS
PLASMA
PLASMA INSTABILITY
PLASMA WAVES
POLARIZATION
SOLAR ACTIVITY
SOLAR CORONA
SOLAR WIND
WAVE PROPAGATION