The wave surveyor technique for fast plasma wave detection in multi-spacecraft data

Abstract

Abstract. Multi-satellite missions like Cluster allow to study the full spatio-temporal variability of plasma processes in near-Earth space, and both the frequency and the wave vector dependence of dispersion relations can be reconstructed. Existing wave analysis methods include high-resolution beamformers like the wave telescope or k-filtering technique, and the phase differencing approach that combines the correlations measured at pairs of sensors of the spacecraft array. In this paper, we make use of the eigendecomposition of the cross spectral density matrix to construct a direct wave identification method that we choose to call the wave surveyor technique. The analysis scheme extracts only the dominant wave mode but is much faster to apply than existing techniques, hence it is expected to ease survey-type detection of waves in large data sets. The wave surveyor technique is demonstrated by means of synthetic data, and is also applied to Cluster magnetometer measurements.

Wave vector analysis methods using multi-point measurements

“…This method directly determines the wave vector associated with the frequency ω is called the wave surveyor technique (Vogt et al, 2008). The wave surveyor technique gives a very similar result in the dispersion relation analysis to that of the wave telescope technique.…”

“…Investigation of the eigenvectors of the CSD matrix represents provides another useful wave vector analysis tools. We present in this section two applications: the wave surveyor technique (Vogt et al, 2008) and the multi-point signal resonator (MSR) technique (Narita et al, 2010b). The former provides a wave vector identification method for the dominant wave components and the latter provides a high-resolution wave number spectrum.…”

“…It can be shown that the wave vector can be directly obtained from the eigenvector phases as (Vogt et al, 2008):…”

“…The wave surveyor technique (Vogt et al, 2008) is a direct identification tool of wave dispersion relations in the sense that the wave vectors are computed directly as a function of the frequencies. The wave telescope technique, in contrast, provides the wave power in the frequency-wave vector domain and one has to search peaks of the energy distribution in the wave vector domain to identify the wave vectors of the dominant wave components, which is computationally demanding.…”

Evaluation of magnetic helicity density in the wave number domain using multi-point measurements in space

“…This effect stems from the inversion of the CSD matrix in Eq. (18), that is the matrix cannot be inverted for a data set with a pure plane wave because at least one eigenvalue in the matrix is very small in such a data set and the inversed matrix diverges (Vogt et al, 2008). (3) Estimate of the helicity density is more stable than that of the energy against noise.…”