Abstract
Abstract. The Spatio Temporal Analysis of Field Fluctuations (STAFF) experiment is one of the five experiments, which constitute the Cluster Wave Experiment Consortium (WEC). STAFF consists of a three-axis search coil magnetometer to measure magnetic fluctuations at frequencies up to 4 kHz, a waveform unit (up to either 10 Hz or 180 Hz) and a Spectrum Analyser (up to 4 kHz). The Spectrum Analyser combines the 3 magnetic components of the waves with the two electric components measured by the Electric Fields and Waves experiment (EFW) to calculate in real time the 5 × 5 Hermitian cross-spectral matrix at 27 frequencies distributed logarithmically in the frequency range 8 Hz to 4 kHz. The time resolution varies between 0.125 s and 4 s. The first results show the capabilities of the experiment, with examples in different regions of the magnetosphere-solar wind system that were encountered by Cluster at the beginning of its operational phase. First results obtained by the use of some of the tools that have been prepared specifically for the Cluster mission are described. The characterisation of the motion of the bow shock between successive crossings, using the reciprocal vector method, is given. The full characterisation of the waves analysed by the Spectrum Analyser, thanks to a dedicated program called PRASSADCO, is applied to some events; in particular a case of very confined electromagnetic waves in the vicinity of the equatorial region is presented and discussed.Key words. Magnetospheric physics (magnetopause, cusp and boundary layer) – Space plasma physics (waves and instabilities; shock waves)
Highlights
The Cluster mission has been designed to study the thin layers of the interaction regions between the solar wind and the Earth’s magnetosphere
Among these tools are the adaptive correlation function method (Rezeau et al, 1998) for the study of very small scale structures (1 s or less), the Field Energy Distribution (FED) method (Pincon and Lefeuvre, 1991) that uses the waveform measurements from the four spacecraft to determine the k vector distribution of the waves and the wave distribution function (WDF) (Lefeuvre et al, 1981) that is determined from the auto- and cross-power spectra at a given spacecraft location
To achieve these objectives much more work has to be done both with the dedicated scientific data analysis programs and with comparison and combination of data coming from the other Cluster instruments
Summary
The Cluster mission has been designed to study the thin layers of the interaction regions between the solar wind and the Earth’s magnetosphere. The purpose of the present paper is to give an overview of the very first observations and indications of how to use some of the specific STAFF data analysis tools to achieve the above objectives, namely how to determine the wave characteristics in the frequency range of the STAFF Spectrum Analyser (10 Hz–4 kHz) with the help of the dedicated PRASSADCO program and how to characterise a shock surface and its velocity using the reciprocal vector method. This is preceded by a short summary of the STAFF instrument characteristics.
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