[P-EM11] Dynamics of the Inner Magnetospheric System

[PEM11-06] Spatial relationship of SAPS and particle boundaries as observed by Arase

*Tomoaki Hori¹, Yoshizumi Miyoshi¹, Satoko Nakamura¹, Yasumasa Kasaba², Tomoko Nakagawa³, Masahiro Kitahara¹, Shoya Matsuda⁵, Nozomu Nishitani¹, Atsushi Kumamoto², Fuminori Tsuchiya², Yoshiya Kasahara⁴, Kazushi Asamura⁵, Chae-Woo Jun¹, Yoichi Kazama⁶, Shiang-Yu Wang⁶, Kunihiro Keika⁷, Satoshi Kasahara⁷, Shoichiro Yokota⁸, Ayako Matsuoka⁹, Iku Shinohara⁵ (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.Planetary Plasma and Atmospheric Research Center, Tohoku University, 3.Information and Communication Engineering, Tohoku Institute of Technology, 4.Kanazawa University, 5.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 6.Academia Sinica Institute of Astronomy and Astrophysics, Taiwan, 7.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 8.Graduate School of Science, Osaka University, 9.Data Analysis Center for Geomagnetism and Space Magnetism, Graduate School of Science, Kyoto University)

Keywords:SAPS, inner magnetosphere, Earth, electric field

Relative displacement of subauroral polarization stream (SAPS) and particle boundaries in the inner magnetosphere is extensively investigated using the particle and field data obtained by the Arase satellite. The two major theoretical paradigms of SAPS, the current generator and the voltage generator models, both attribute the source of the poleward electric field (E-field) to a latitudinal (radial in the magnetosphere) gap between the ion and electron plasma sheets (PS). Indeed, the enhancement of electric field is frequently observed around the intermediate region between the two PS along inner magnetosphere passes of Arase in the evening-to-midnight sector. A close examination of the Arase observations, however, reveals that their relative position varies significantly from event to event: the radially-inner boundary of SAPS, for example, can form either in the intermediate region or at a further inward location of the PS gap. The plasmapause, as identified by the plasma wave observations, can appear either at the SAPS inner edge or at a further outward point. It is also found that most of the events show a broader radial width of SAPS E-field than the ion-electron PS gap. We discuss possible scenarios that can explain the variety of the spatial relationship of SAPS with both the PS and plasmapause.