Dispersion relation analysis of turbulent magnetic field fluctuations in fast solar wind

• Published in: Annales geophysicae (1988) Vol. 31; no. 11; pp. 1949 - 1955
• Main Authors: Perschke, C., Narita, Y., Gary, S. P., Motschmann, U., Glassmeier, K.-H.
• Format: Journal Article
• Language: English
• Published: Copernicus GmbH 15.11.2013; Copernicus Publications
• Subjects: Analysis; Magnetic fields; Turbulence (Fluid dynamics)
• ISSN: 1432-0576; 0992-7689; 1432-0576
• DOI: 10.5194/angeo-31-1949-2013

Physical processes of the energy transport in solar wind turbulence are a subject of intense studies, and different ideas exist to explain them. This manuscript describes the investigation of dispersion properties in short-wavelength magnetic turbulence during a rare high-speed solar wind event with a flow velocity of about 700 km s−1 using magnetic field and ion data from the Cluster spacecraft. Using the multi-point resonator technique, the dispersion relations (i.e., frequency versus wave-number values in the solar wind frame) of turbulent magnetic fluctuations with wave numbers near the inverse ion inertial length are determined. Three major results are shown: (1) the wave vectors are uniformly quasi-perpendicular to the mean magnetic field; (2) the fluctuations show a broad range of frequencies at wavelengths around the ion inertial length; and (3) the direction of propagation at the observed wavelengths is predominantly in the sunward direction. These results suggest the existence of high-frequency dispersion relations partly associated with normal modes on small scales. Therefore nonlinear energy cascade processes seem to be acting that are not described by wave–wave interactions.