Density Fluctuations in the Solar Wind Driven by Alfvén Wave Parametric Decay

Abstract

Measurements and simulations of inertial compressive turbulence in the solar wind are characterized by anti-correlated magnetic fluctuations parallel to the mean field and density structures. This signature has been interpreted as observational evidence for non-propagating pressure balanced structures (PBS), kinetic ion acoustic waves, as well as the MHD slow-mode. Given the high damping rates of parallel propagating compressive fluctuations, their ubiquity in satellite observations is surprising, and suggestive of a local driving process. One possible candidate for the generation of compressive fluctuations in the solar wind is Alfvén wave parametric instability. Here we test the parametric decay process as a source of compressive waves in the solar wind by comparing the collisionless damping rates of compressive fluctuations with the growth rates of the parametric decay instability daughter waves. Our results suggest that generation of compressive waves through parametric decay is overdamped at 1 AU, but that the presence of slow-mode like density fluctuations is correlated with the parametric decay of Alfvén waves.

References in corpus (3)

• Anisotropic scaling of magnetohydrodynamic turbulence
• The parametric instability of Alfvén waves: effects of temperature anisotropy
• The Parametric Decay Instability of Alfven waves in Turbulent Plasmas and the Applications in the Solar Wind

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