Decay instability of incoherent Alfven waves in the solar wind

Journal Article · Sun Mar 01 00:00:00 EST 1992 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JA02967· OSTI ID:5595189

Umeki, H; Terasawa, T ^[1]

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1. Kyoto Univ. (Japan)

The nonlinear evolution of a large-amplitude incoherent Alfven wave is studied via one-dimensional magnetohydrodynamic simulation. The initial wave magnetic field is given as a superposition of circularly polarized Alfven waves with the same helicity and propagation direction but with different wave numbers. What the authors observe is contrary to the previous belief that incoherent Alfven waves are stable against decay: in a low {beta} plasma ({beta} = 0.2) one can clearly see the growth of backscattered Alfven waves, which are opposite in helicity and propagation direction from the original Alfven waves. In a high {beta} plasma ({beta} = 2.0), on the other hand, no backscattered Alfven waves are observed. These results are consistent with the expectation from the theory of the parametric decay instability developed for a coherent Alfven wave. They also show that incoherent Alfven waves in the solar wind can decay parametrically in the region of 4-20 R{sub S} where {beta} is sufficiently low. For the decay process to work, the period of Alfven waves should be less than several minutes.

• OSTI ID: 5595189
• Journal Information: Journal of Geophysical Research; (United States), Vol. 97:A3; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
SOLAR WIND
ALFVEN WAVES
DECAY INSTABILITY
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
NONLINEAR PROBLEMS
PARAMETRIC INSTABILITIES
PLASMA SIMULATION
WAVE PROPAGATION
FLUID MECHANICS
HYDRODYNAMICS
HYDROMAGNETIC WAVES
INSTABILITY
MECHANICS
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
SIMULATION
SOLAR ACTIVITY
661320* - Auroral
Ionospheric
& Magnetospheric Phenomena- (1992-)