Authors

L. R. Lyons 1, T. Nagai 2, G. T. Blanchard 1,J. C. Samson 3, 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

J. Geophys. Res., 104, 4485-4500, 1999

Abstract

Poleward boundary intensifications are nightside geomagnetic disturbances that have an auroral signature that moves equatorward from the poleward boundary of the auroral zone. They occur repetitively, so that many individual disturbances can occur during time intervals of ~ 1 hr, and they appear to be the most intense auroral disturbance at times other than the expansion phase of substorms. We have used data from three nightside conjunctions of the Geotail spacecraft in the magnetotail with the CANOPUS ground-based array in central Canada to investigate the relation between the poleward boundary intensifications and bursty plasma-sheet flows and to characterize the bursty flows associated with the disturbances. We have found a distinct difference in plasma sheet dynamics between periods with, and periods without, poleward boundary intensifications. During periods with identifiable poleward boundary intensifications, the plasma sheet has considerable structure and bursty flow activity. During periods without such poleward boundary intensifications, the plasma sheet was found to be far more stable with fewer and weaker bursty flows. This is consistent with the intensifications being the result of the mapping to the ionosphere of the electric fields that give rise to bursty flows within the plasma sheet. Two different types of plasma sheet disturbance have been found to be associated with the poleward boundary intensifications. The first consists of plasma sheet flows that appear to be the result of Speiser motion of particles in a localized region of thin current sheet. The second, seen primarily in our nearest-to-the-Earth example, consists of energy dispersed ion structures that culminate in bursts of low energy ions and isotropic low-energy electrons and are associated with minima in magnetic field and temperature and maxima in ion density and pressure. Both types of plasma sheet disturbance are associated with localized regions of enhanced dawn-to-dusk electric fields and appear to be associated with localized enhanced reconnection.

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: 1-3, 4-5, 6-9, 10-11(PDF format)