Authors

L. R. Lyons 1, T. Nagai 2, J. C. Samson 3, E. Zesta 1, T. Yamamoto 4, T, Mukai 4, A. Nishida 4,, S. Kokubun 5

1  Department of Atmospheric Sciences
University of California, Los Angeles
Los Angeles, CA 90095-1565

2  Department of Earth and Planetary Sciences
Tokyo Institute of Technology
Ookayama 2-12-1, Meguro
Tokyo 152-8551, Japan

3  Department of Physics
University of Alberta
Edmonton, Alberta, T6G 2E9

4  Institute of Space and Astronautical Science
3-1-1 Yoshinodai, Sagamihara
Kanagawa 229-8510, Japan

5  Solar-Terrestrial Environment Laboratory
Nagoya University
Honohara 3-13, Toyokawa
Aichi 442-8507, Japan

Magnetospheric Current Systems, ed. by S. Ohtani and R. L. Lysak, American Geophysical Union, Washington, p. 267, 2000.

Abstract

Flow in the tail often consists of highly structured bursts. Here we use Geotail spacecraft data to show that bursty flows in the tail are associated with significant (~5 nT) magnetic structure indicating structured currents with estimated densities of > 1 x 10^-10 A/m². When mapped along field lines to the auroral ionosphere, these currents appear to be sufficiently intense ( 1 x 10^-6 A/m²) to account for auroral poleward boundary intensifications, which are nightside geomagnetic disturbances having an auroral signature that moves equatorward from the poleward boundary of the auroral oval. Our analysis suggests that there is a dramatic difference between two states of the tail plasma sheet: a stable state with a minimum of bursty flow activity and associated structured currents and a turbulent state with considerable bursty flow activity and structured currents. The transition between these two states can be quite abrupt; however intermediate states also exist. Structured currents appear to be just as important a part of the turbulent plasma sheet as are the bursty flows, so that the concept of a stable tail current distribution may not be appropriate when the plasma sheet is in its turbulent state. We furthermore find that significant flows and structured currents, when present, appear to exist throughout the entire height of the tail plasma sheet during the turbulent periods, suggesting that it may generally be inappropriate to separate plasma sheet flows within the central plasma sheet from those within plasma sheet boundary layer. We also find that dipolarizations of the magnetic field do not accompany the majority of flow burst events that we have examined. However, dipolarizations are occasionally seen, primarily during substorm associated bursty flow activity.

All full manuscripts and figures are available in PDF format only. For another format or hardcopies you will need to contact the Authors.

Paper (pdf format)
Figures: 1-4 and 5-8(PDF format)