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

Read Full Article (file size: 2104232 bytes)    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, A04215, doi:10.1029/2005JA011545, 2006

Equatorial distributions of the plasma sheet ions, their electric and magnetic drifts, and magnetic fields under different interplanetary magnetic field Bz conditions

Chih-Ping Wang

Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, USA


Larry R. Lyons

Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, USA


James M. Weygand

Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California, USA


Tsugunobu Nagai

Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan


Richard W. McEntire

Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA


Abstract

To understand the nightside plasma sheet structure under different interplanetary magnetic field (IMF) B z conditions, we have investigated statistically the equatorial distributions of ions and magnetic fields from Geotail when the IMF has been continuously northward or southward for shorter or longer than 1 hour. A dawn-dusk density (temperature) asymmetry with higher density (temperature) on the dawn (dusk) side is seen in the near-Earth plasma sheet during northward IMF, resulting in roughly dawn-dusk symmetric pressure. As southward IMF proceeds, the density asymmetry weakens while the temperature asymmetry maintains, resulting in higher pressure on the dusk side. The plasma sheet is relatively colder and denser near the flanks than around midnight. The flux distributions show that the density asymmetry is due to ions <∼3 keV, and the temperature asymmetry is due to ions above thermal energy. The perpendicular flow shows that ions divert around the Earth mainly through the dusk side in the inner plasma sheet because of westward diamagnetic drift. The magnetic fields indicate that field lines are more stretched during southward IMF. Ions' electric and magnetic drift paths evaluated from the observations show that for thermal energy ions, magnetic drift is as important as electric drift. Comparison of the distributions of the observed phase space density with the evaluated drift paths at different energies indicates that the electric and magnetic drift transport is responsible for the observed dawn-dusk asymmetries in the plasma sheet structure.

Received 22 November 2005; accepted 19 January 2006; published 21 April 2006.

Keywords: IMF; ions; plasma sheet.

Index Terms: 2764 Magnetospheric Physics: Plasma sheet; 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions; 2740 Magnetospheric Physics: Magnetospheric configuration and dynamics; 2760 Magnetospheric Physics: Plasma convection (2463); 2744 Magnetospheric Physics: Magnetotail.

Read Full Article (file size: 2104232 bytes)    Cited by

Citation: Wang, C.-P., L. R. Lyons, J. M. Weygand, T. Nagai, and R. W. McEntire (2006), Equatorial distributions of the plasma sheet ions, their electric and magnetic drifts, and magnetic fields under different interplanetary magnetic field Bz conditions, J. Geophys. Res., 111, A04215, doi:10.1029/2005JA011545.