The slow-mode nature of compressible wave power in solar wind turbulence

G. G. Howes, S. D. Bale, K. G. Klein, C. H.K. Chen, C. S. Salem, J. M. Tenbarge

Research output: Contribution to journalArticle

103 Scopus citations

Abstract

We use a large, statistical set of measurements from the Wind spacecraft at 1 AU, and supporting synthetic spacecraft data based on kinetic plasma theory, to show that the compressible component of inertial range solar wind turbulence is primarily in the kinetic slow mode. The zero-lag cross-correlation C(δn, δB) between proton density fluctuations δn and the field-aligned (compressible) component of the magnetic field δB is negative and close to -1. The typical dependence of C(δn, δB) on the ion plasma beta βi is consistent with a spectrum of compressible wave energy that is almost entirely in the kinetic slow mode. This has important implications for both the nature of the density fluctuation spectrum and for the cascade of kinetic turbulence to short wavelengths, favoring evolution to the kinetic Alfvén wave mode rather than the (fast) whistler mode.

Original languageEnglish (US)
Article numberL19
JournalAstrophysical Journal Letters
Volume753
Issue number1
DOIs
StatePublished - Jul 1 2012

Keywords

  • solar wind
  • turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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