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Nonlinear astrophysical Alfvén waves: onset and outcome of the modulational instability
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Nonlinear astrophysical Alfvén waves: onset and outcome of the modulational instability

S. R Spangler
The Astrophysical journal, Vol.299(1), pp.122-137
1985
DOI: 10.1086/163686

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Abstract

A numerical study has been made of the nonlinear development of Alfvén waves, with application to Alfvén waves in astrophysical plasmas. The waves are modeled by the derivative nonlinear Schrödinger equation. This paper studies the evolution of initial conditions consisting of (1) amplitude-modulated wave packets and (2) broad-band Alfvénic noise. Dependent on the polarization of the Alfvén wave, a strong modulational collapse instability results in which a wave packet becomes more intense and of smaller spatial extent. The intensification of the wave packet is halted by the formation of solitons, so the asymptotic state of the instability consists of propagating soliton-like pulses. The author discusses application to several astrophysical settings, such as Earth's bow shock region, the interstellar medium adjacent to a supernova remnant, and extragalactic radio sources.
Astronomy Earth, ocean, space Exact sciences and technology Fundamental aspects of astrophysics Fundamental astronomy and astrophysics. Instrumentation, techniques, and astronomical observations Magnetohydrodynamics and plasmas

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