Plasma sheet turbulence observed by Cluster II

Abstract

[1] Cluster fluxgate magnetometer (FGM) and ion spectrometer (CIS) data are employed to analyze magnetic field fluctuations within the plasma sheet during passages through the magnetotail region in the summers of 2001 and 2002 and, in particular, to look for characteristics of magnetohydrodynamic (MHD) turbulence. Power spectral indices determined from power spectral density functions are on average larger than Kolmogorov's theoretical value for fluid turbulence as well as Kraichnan's theoretical value for MHD plasma turbulence. Probability distribution functions of the magnetic fluctuations show a scaling law over a large range of temporal scales with non-Gaussian distributions at small dissipative scales and inertial scales and more Gaussian distribution at large driving scales. Furthermore, a multifractal analysis of the magnetic field components shows scaling behavior in the inertial range of the fluctuations from about 20 s to 13 min for moments through the fifth order. Both the scaling behavior of the probability distribution functions and the multifractal structure function suggest that intermittent turbulence is present within the plasma sheet. The unique multispacecraft aspect and fortuitous spacecraft spacing allow us to examine the turbulent eddy scale sizes. Dynamic autocorrelation and cross correlation analysis of the magnetic field components allow us to determine that eddy scale sizes fit within the plasma sheet. These results suggest that magnetic field turbulence is occurring within the plasma sheet resulting in turbulent energy dissipation.

Double rank-ordering technique of ROMA (Rank-Ordered Multifractal Analysis) for multifractal fluctuations featuring multiple regimes of scales

“…Such has been the case, for instance, for the measured fields in the solar wind, magnetospheric cusp, plasma sheet and the auroral zone (Burlaga, 1991;Bruno et al, 2001;Weygand et al, 2005;Tam et al, 2005;Echim et al, 2007). The origin of intermittent fluctuations in magnetized plasmas was interpreted as the result Correspondence to: S. W. Y.…”

Magnetic Turbulence Associated with Magnetic Dipolarizations in the Near-Tail of the Earth's Magnetosphere: Test of Anisotropy

“…2 shows the scatter plots of the spectral indices α for all of the 47 events. The indices are presented for three pairs of two different components, so that a degree of anisotmulti-spacecraft observations from Cluster, Weygand et al (2005) were able to estimate turbulent eddy scale sizes in association with magnetic field fluctuations in the plasma sheet. Voros et al (2004) introduced a wavelet technique to study magnetic turbulence, as obtained from the same Cluster satellite observations.…”

Intermittency of storms and substorms: is it related to the critical behaviour?

“…Stepanova et al, (2005aStepanova et al, ( , 2005b have found that the intermittency has strong magnetic local time behaviour being significantly stronger close to the substorm eye. Weygand et al (2005) have also found that both the scaling behavior of the probability distribution functions and the multifractal structure function suggest that intermittent MHD turbulence is present within the plasma sheet. This paper strives to look at the intermittency of the magnetospheric dynamics from a slightly different angle.…”