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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, A05211, doi:10.1029/2007JA012789, 2008

Cluster observations of electrostatic solitary waves near the Earth's bow shock

Y. Hobara

Automatic Control and Systems Engineering, University of Sheffield, UK


S. N. Walker

Automatic Control and Systems Engineering, University of Sheffield, UK


M. Balikhin

Automatic Control and Systems Engineering, University of Sheffield, UK


O. A. Pokhotelov

Automatic Control and Systems Engineering, University of Sheffield, UK


M. Gedalin

Department of Physics, Ben-Gurion University, Beer-Sheva, Israel


V. Krasnoselskikh

Laboratoire de Physique et Chimie de l'Environnement, CNRS, Orleans, France


M. Hayakawa

Swedish Institute of Space Physics, Uppsala, Sweden


M. André

Department of Electronic Engineering, University of Electro-Communications, Tokyo, Japan


M. Dunlop

Space Science Division, Rutherford Appleton Laboratory, UK


H. Rème

CESR/CNRS, Toulouse, France


A. Fazakerley

Mullard Space Science Laboratory, University College London, London, UK


Abstract

Using a period of internal burst mode data from the Cluster Electric Field and Wave instrument a number of electrostatic solitary structures have been identified in the foot region of Earth's quasi-perpendicular bow shock. The four individual probe potential measurements are utilized to investigate the fundamental characteristics of the solitary wave structures such as wave propagation vector, propagation velocity, scale-size and potential amplitude. Two classes of waves are observed. Bipolar solitary waves typically propagate in the solar wind direction toward the shock but at a significant angle from the ambient magnetic field. Unipolar/tripolar solitary waves tend to propagate along the ambient magnetic field. The wave amplitude-scale size relation is similar to that obtained for similar structures observed in the auroral zone. The structures lie in the theoretically allowed region in width-amplitude space to be consistent with the BGK ion holes. Using a period of internal burst mode data from the Cluster Electric Field and Wave instrument a number of electrostatic solitary structures have been identified in the foot region of Earth's quasi-perpendicular bow shock. The four individual probe potential measurements are utilized to investigate the fundamental characteristics of the solitary wave structures such as wave propagation vector, propagation velocity, scale-size and potential amplitude. Two classes of waves are observed. Bipolar solitary waves typically propagate in the solar wind direction toward the shock but at a significant angle to the ambient magnetic field in contrast to most previous studies which assume parallel propagation to the ambient magnetic field. In contrast, unipolar/tripolar solitary waves tend to propagate along the ambient magnetic field. The wave amplitude-scale size relation is similar to that obtained for structures observed in the auroral zone. The structures lie in the theoretically allowed region in width-amplitude space to be consistent with the BGK (Bernstein-Greene-Kruskal) ion holes. The two classes of observed solitary waves may greatly influence the ambient plasma dynamics around the shock. The bipolar solitary waves do not exhibit a large net potential difference but may still play an important role in plasma thermalisation by particle scattering. Unipolar/tripolar solitary waves exhibit a remarkable net potential difference that may be responsible for the plasma energisation along the ambient magnetic field.

Received 4 September 2007; accepted 14 January 2008; published 10 May 2008.

Keywords: Solitary waves; bow shock; BGK.

Index Terms: 7803 Space Plasma Physics: Active perturbation experiments; 7852 Space Plasma Physics: Solitons and solitary waves (4455); 2154 Interplanetary Physics: Planetary bow shocks; 7815 Space Plasma Physics: Electrostatic structures; 4455 Nonlinear Geophysics: Nonlinear waves, shock waves, solitons (0689, 2487, 3280, 3285, 4275, 6934, 7851, 7852).

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 538053 bytes)

Citation: Hobara, Y., et al. (2008), Cluster observations of electrostatic solitary waves near the Earth's bow shock, J. Geophys. Res., 113, A05211, doi:10.1029/2007JA012789.