Current sheet structures and particle properties near the tail reconnection
region

R. Nakamura, Y. Asano, S. Imada, C. Mouikis, L. M. Kistler, B. Klecker, T. Nagai, C. J. Owen, A. Balogh, H. Reme, P. Daly,  J. Quinn, G. Paschmann, A. N. Fazerkerley, A. Runov, W. Baumjohann,  M. Hoshino  

The tail current sheet and its dynamics are one of the most essential elements in magnetospheric physics. Multipoint observation of Cluster with spatial scale varying from 250 km to 4000 km enabled us to resolve current structeres and relevant particle behaviour near the the reconnection region. In this paper, we present X-line observations from different Cluster tetrahedron scales to highlight the dynamics of the current sheet near the reconnection region. In 2001, when the Cluster tetrahedron scale was 2000 km, it was shown that thin current sheets, with a spatial scale comparable to the ion inertia length, and off-equatorial current sheets (or bifurcated current sheets) do exist near the diffusion region. The observations from 2003 with tetrahedron scale about 250 km allowed us then to resolve the detailed features of these thin current sheet using curlometer technique.  We further examine the particle behaviour relevant to these current sheets to discussed on the current carriers and on the particle acceleration in the vicinity of the X-line.