ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-26-2503-2008 Correlation length of magnetosheath fluctuations: Cluster statistics Gutynska O. 1 Šafránková J. 1 Němeček Z. 1 Charles University, Faculty of Mathematics and Physics, V Holesovickach 2, 180 00 Praha 8, Czech Republic 01 09 2008 26 9 2503 2513 Copyright: © 2008 O. Gutynska et al. 2008 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/26/2503/2008/angeo-26-2503-2008.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/26/2503/2008/angeo-26-2503-2008.pdf

Magnetosheath parameters are usually described by gasdynamic or magnetohydrodynamic (MHD) models but these models cannot account for one of the most important sources of magnetosheath fluctuations – the foreshock. Earlier statistical processing of a large amount of magnetosheath observations has shown that the magnetosheath magnetic field and plasma flow fluctuations downstream of the quasiparallel shock are much larger than those at the opposite flank. These studies were based on the observations of a single spacecraft and thus they could not provide full information on propagation of the fluctuations through the magnetosheath. <br><br> We present the results of a statistical survey of the magnetosheath magnetic field fluctuations using two years of Cluster observations. We discuss the dependence of the cross-correlation coefficients between different spacecraft pairs on the orientation of the separation vector with respect to the average magnetic field and plasma flow vectors and other parameters. We have found that the correlation length does not exceed ~1 <I>R<sub>E</sub></I> in the analyzed frequency range (0.001–0.125 Hz) and does not depend significantly on the magnetic field or plasma flow direction. A close connection of cross-correlation coefficients computed in the magnetosheath with the cross-correlation coefficients between a solar wind monitor and a magnetosheath spacecraft suggests that solar wind structures persist on the background of magnetosheath fluctuations.

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