Non-Gaussian statistics in space plasma turbulence, fractal properties and pitfalls

Magnetic field fluctuations in the vicinity of the Earth's bow shock have been investigated with the aim to characterize the intermittent behaviour of strong plasma turbulence. The observed small-scale intermittency may be the signature of a multifractal process but a deeper inspection reveals caveats in such an interpretation. Several effects, including the anisotropy of the wavefield, the violation of the Taylor hypothesis and the occasional occurrence of coherent wave packets, strongly affect the higher order statistical properties. After correcting these effects, a more Gaussian and scale-invariant wavefield is recovered.Comment: 13 pages (including 13 postscript figures), to appear in Nonlinear Processes in Geophysic

Identifying nonlinear wave interactions in plasmas using two-point measurements: a case study of Short Large Amplitude Magnetic Structures (SLAMS)

A framework is described for estimating Linear growth rates and spectral energy transfers in turbulent wave-fields using two-point measurements. This approach, which is based on Volterra series, is applied to dual satellite data gathered in the vicinity of the Earth's bow shock, where Short Large Amplitude Magnetic Structures (SLAMS) supposedly play a leading role. The analysis attests the dynamic evolution of the SLAMS and reveals an energy cascade toward high-frequency waves.Comment: 26 pages, 13 figure

On aspects of the measurement of non-linear turbulence processes using the cluster wave experiments

International audienceThe ESA/NASA Cluster mission has four identical satellites and is due for launch at the end of 1995. It will provide a unique opportunity to study medium scale processes in the region from inside the magnetopause to the solar wind. The polar orbit will allow measurements in the cusp and along auroral field lines, both regions where turbulence is to be expected. Five of the eleven instruments on each payload form the Wave Experiment Consortium (WEC); EFW, STAFF, VMISPER, WBD and DWP. The WEC is capable of a wide variety of wave and turbulence measurements. This paper outlines these capabilities and describes the form of the data which will be collected. The paper gives a discussion of how the WEC data may be analysed so as to give an insight into the non-linear processes which occur in these regions of the space plasmas. There are many ways in which a plasma may be considered to behave in a non-linear manner. We concentrate on how the spatio-temporal turbulence in the plasma may be investigated so as to yield the energy spectrum with respect to both the frequency and wave number

Determination of dispersion relations in quasi-stationary plasma turbulence using dual satellite data

International audienceThe joint frequency-wavenumber spectrum is one of day 304 of 1984. This data set has already been discussed in the basic quantities for analyzing plasma turbulence. It is shown how the full spectrum can be recovered from wavefields measured by two or more satellites via spectral methods based on wavelet transforms. Compared to standard cross-correlation techniques, different branches in the dispersion relation can be resolved and quasi-stationary wavefields can be accessed. Using this new approach, low frequency magnetic field data from the [Schwartz et al., 1992; Mann et al., 1994]. The turbulence in the foreshock region reveals a great variety of wave phenomena, among which solitary structures termed Short Large Amplitude Magnetic Structures (SLAMS) [Schwartz et al., 1992] have received much attention. The SLAMS, which are a subset of more general pulsations [Thomson et al., 1990] and which are related to kinetic magnetosonic waves [Omidi et al., 1990] and to AMPTE-UKS and AMPTE-IRM spacecraft are investigated and soliton Alfv6n waves [Hada et al., 1989], try to propagate the impact of nonlinear processes on wave propagation at the Earth's foreshock is revealed

On aspects of the measurement of non-linear turbulence processes using the cluster wave experiments

The ESA/NASA Cluster mission has four identical satellites and is due for launch at the end of 1995. It will provide a unique opportunity to study medium scale processes in the region from inside the magnetopause to the solar wind. The polar orbit will allow measurements in the cusp and along auroral field lines, both regions where turbulence is to be expected. Five of the eleven instruments on each payload form the Wave Experiment Consortium (WEC); EFW, STAFF, VMISPER, WBD and DWP. The WEC is capable of a wide variety of wave and turbulence measurements. This paper outlines these capabilities and describes the form of the data which will be collected. The paper gives a discussion of how the WEC data may be analysed so as to give an insight into the non-linear processes which occur in these regions of the space plasmas. There are many ways in which a plasma may be considered to behave in a non-linear manner. We concentrate on how the spatio-temporal turbulence in the plasma may be investigated so as to yield the energy spectrum with respect to both the frequency and wave number

Transport and self-organization in dissipative drift-wave turbulence

International audienceAbstract. The ESA/NASA Cluster mission has four identical satellites and is due for launch at the end of 1995. It will provide a unique opportunity to study medium scale processes in the region from inside the magnetopause to the solar wind. The polar orbit will allow measurements in the cusp and along auroral field lines, both regions where turbulence is to be expected. Five of the eleven instruments on each payload form the Wave Experiment Consortium (WEC); EFW, STAFF, VMISPER, WBD and DWP. The WEC is capable of a wide variety of wave and turbulence measurements. This paper outlines these capabilities and describes the form of the data which will be collected. The paper gives a discussion of how the WEC data may be analysed so as to give an insight into the non-linear processes which occur in these regions of the space plasmas. There are many ways in which a plasma may be considered to behave in a non-linear manner. We concentrate on how the spatio-temporal turbulence in the plasma may be investigated so as to yield the energy spectrum with respect to both the frequency and wave number