Multi-scale analysis of compressible fluctuations in the solar wind

• Published in: Annales geophysicae (1988) Vol. 36; no. 1; pp. 47 - 52
• Main Authors: Roberts, Owen W., Narita, Yasuhito, Escoubet, C.-Philippe
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 12.01.2018; Copernicus Publications
• Subjects: Alfven waves; Analysis; Compressibility; Correlation; Correlation analysis; Electron density; Field strength; Fluctuations; Frequency ranges; Helicity; Magnetic field; Magnetic fields; Magnetic properties; Magnetohydrodynamic turbulence; Multiscale analysis; Physics; Plasma; Plasma turbulence; Plasmas (physics); Protons; Solar wind; Turbulence; Wave packets; Wave propagation
• ISSN: 1432-0576; 0992-7689; 1432-0576
• DOI: 10.5194/angeo-36-47-2018

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. Keywords. Interplanetary physics (MHD waves and turbulence)