American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 549248 bytes)    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, A01203, doi:10.1029/2005JA011231, 2006

Low-frequency wave characteristics in the upstream and downstream regime of the terrestrial bow shock

Y. Narita

Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Braunschweig, Germany


K.-H. Glassmeier

Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Braunschweig, Germany
Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany


K.-H. Fornaçon

Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Braunschweig, Germany


I. Richter

Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Braunschweig, Germany


S. Schäfer

Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Braunschweig, Germany


U. Motschmann

Institut für Theoretische Physik, Technische Universität Braunschweig, Braunschweig, Germany


I. Dandouras

Centre d'Etude Spatiale des Rayonnements, Centre National de la Recherche Scientifique, Toulouse, France


H. Rème

Centre d'Etude Spatiale des Rayonnements, Centre National de la Recherche Scientifique, Toulouse, France


E. Georgescu

Max-Planck-Institut für extraterrestrische Physik, Garching, Germany


Abstract

Collisionless shocks in space are accompanied by the low-frequency waves of the magnetic field both upstream and downstream of the shock. However, characteristics of these waves in the plasma rest frame are poorly understood, since spatial scale such as wavelength is hardly determined using single or at best two spacecraft observations. Taking advantage of multipoint measurements of the Cluster spacecraft, we present a statistical study to reveal the rest frame properties of the waves in the terrestrial bow shock environment such as frequencies, wave numbers, phase velocities, propagation directions, polarization and transport ratios for the quasi-parallel and the quasi-perpendicular shock regimes and in the upstream region, the outer, the middle, and the inner magnetosheath. We find that the quasi-parallel shock upstream waves (or the foreshock waves) exhibit properties of the fast mode wave excited by the ion beam instability. Upstream of the quasi-perpendicular shock the waves also exhibit similar properties to the foreshock waves, but the wave mode identification needs further investigations. In the magnetosheath the waves exhibit properties which are persistent from the outer to the inner magnetosheath. They can be interpreted as the mirror mode coupled to the plasma inhomogeneity or as the slow mode. We also find an organization in the wave propagation pattern that the upstream waves propagate toward upstream, while the magnetosheath waves propagate toward the flank region and toward the magnetopause. It is concluded that wave properties are different between the upstream and the downstream regions, but they are similar between the quasi-parallel and the quasi-perpendicular shock regimes, suggesting that the upstream waves are not transmitted to the downstream region across the shock and that the downstream waves do not depend on the shock angle (between the upstream magnetic field and the shock normal direction).

Received 13 May 2005; accepted 2 November 2005; published 14 January 2006.

Keywords: shock upstream and downstream waves; wave modes; propagation pattern.

Index Terms: 2159 Interplanetary Physics: Plasma waves and turbulence; 2154 Interplanetary Physics: Planetary bow shocks; 2772 Magnetospheric Physics: Plasma waves and instabilities (2471); 0689 Electromagnetics: Wave propagation (2487, 3285, 4275, 4455, 6934).

Read Full Article (file size: 549248 bytes)    Cited by

Citation: Narita, Y., K.-H. Glassmeier, K.-H. Fornaçon, I. Richter, S. Schäfer, U. Motschmann, I. Dandouras, H. Rème, and E. Georgescu (2006), Low-frequency wave characteristics in the upstream and downstream regime of the terrestrial bow shock, J. Geophys. Res., 111, A01203, doi:10.1029/2005JA011231.