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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 36, issue 1 | Copyright
Ann. Geophys., 36, 47-52, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

ANGEO Communicates 12 Jan 2018

ANGEO Communicates | 12 Jan 2018

Multi-scale analysis of compressible fluctuations in the solar wind

Owen W. Roberts1, Yasuhito Narita2, and C.-Philippe Escoubet1 Owen W. Roberts et al.
  • 1ESA/ESTEC SCI-S, Keplerlaan 1, 2201 AZ, Noordwijk, the Netherlands
  • 2Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, 8042 Graz, Austria

Abstract. Compressible plasma turbulence is investigated in the fast solar wind at proton kinetic scales by the combined use of electron density and magnetic field measurements. Both the scale-dependent cross-correlation (CC) and the reduced magnetic helicity (σm) are used in tandem to determine the properties of the compressible fluctuations at proton kinetic scales. At inertial scales the turbulence is hypothesised to contain a mixture of Alfvénic and slow waves, characterised by weak magnetic helicity and anti-correlation between magnetic field strength B and electron density ne. At proton kinetic scales the observations suggest that the fluctuations have stronger positive magnetic helicities as well as strong anti-correlations within the frequency range studied. These results are interpreted as being characteristic of either counter-propagating kinetic Alfvén wave packets or a mixture of anti-sunward kinetic Alfvén waves along with a component of kinetic slow waves.

Publications Copernicus
Short summary
To investigate compressible plasma turbulence in the solar wind on proton kinetic scales, a high time resolution measurement of the density is obtained from the spacecraft potential. Correlation between the magnetic field strength and the density is investigated as is the rotation sense of the magnetic field. The analysis reveals that compressible fluctuations are characteristic of kinetic Alfvén waves or a mixture of kinetic Alfvén and kinetic slow waves which counter-propagate.
To investigate compressible plasma turbulence in the solar wind on proton kinetic scales, a high...