Volume 110, Number 1, April 2015
|Number of page(s)||6|
|Section||Geophysics, Astronomy and Astrophysics|
|Published online||20 April 2015|
Multipoint observation of anisotropy and intermittency in solar-wind turbulence
1 Swedish Institute of Space Physics - Uppsala, Sweden
2 Dipartimento di Fisica, Università della Calabria - Ponte P. Bucci Cubo 31C, 87036 Rende, Italy
3 NanoTec CNR, U.O. di Cosenza - Ponte P. Bucci Cubo 31C, 87036 Rende, Italy
Received: 27 January 2015
Accepted: 30 March 2015
Using high-resolution magnetic-field Cluster observations, we have investigated the magnetic-field anisotropy via the second- and fourth-order structure functions over a wide range of scales reaching below the subproton scale. The magnetic-field increments have been computed from single- and two-spacecraft measurements. The two-satellite technique allows us to study the increments as a function of an actual space lag. Both single- and two-point analyses show that the magnetic field is anisotropic even at small time/spatial scales. The single-spacecraft data also shows that the degree of anisotropy does not change with the scale at proton and subproton scales. It is also pointed out that the degree of magnetic-field anisotropy tends to be overestimated in the single-spacecraft data analysis. This is particularly evident at small scales and it depends on the angle between the spacecraft separation and the flow direction. From the fourth-order moment of the probability density function of the magnetic-field increments we have also investigated the presence of intermittency in the fluctuations. Even though to a different degree, intermittency was present over the entire range of scales, with an indication of scale invariance at subproton scales.
PACS: 96.50.Ci – Solar wind plasma; sources of solar wind / 95.30.Qd – Magnetohydrodynamics and plasmas / 52.35.Ra – Plasma turbulence
© EPLA, 2015
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