Obervations of current sheet flapping associated with high speed flow in the magnetotail

The magnetotail current sheet frequently moves in the north-south direction, which named current sheet flapping. A statistical survey of Geotail data showed that the flapping motions of the current sheet might be related to the plasma bursty bulk flows BBFs. Current sheet flapping association with fast plasma flows in the plasma sheet and Pi2 pulsation was also observed by THEMIS observations. These observations also pointed out the close relationship between current sheet flapping and the Z component of the ion flow velocity. During the repeated crossings of the current sheet by the spacecraft, the ion velocity V-z showed obviously periodic oscillations. In this observation, the single case will be discussed to reveal that the associated observation BBFs may be the local ions flow. The Cluster FGM, CIS, PEACE and RAPID data will be used to analyze the current sheet flapping case. The CL soft will be used to calculate the current. In the magnetotail, on Oct 26 2002 the Cluster crosses southward the central current sheet in a distance of 19 R-E to Earth. The current sheet flapping case associated by high speed ions flow was observed by Cluster on Oct 26 2002. This flapping case periodic is very good. The FFT analyses show the period of the current sheet flapping is about 2 min, the amplitude is about 20 nT. The velocity values changed periodically. The X component of ions velocity reaches 400 km . s(-1). The Z component of ion velocity is up to 600 km . s(-1). The energy range from 50 similar to 100 keV electrons and 10 keV ions flux is enhanced during the spacecrafts across current sheet center. When the spacecrafts move to the current sheet boundary, the energy of ions and electrons flux is decreasing. The current density is also flapping periodically. The velocity vector distribution show the particles motion is not a single direction. Base on the velocity and current vector analyses, the local particles motion is vortex motion. This current sheet flapping is highly cyclical event and lasts for about 10 minutes. Through the particle and current density characters analyses, the high speed flows is local particles velocity. The present result indicated that the high speed ion flow is local particles motion, not come from far away magnetail. This result show the current sheet flapping may be induced by a self-circulation process not the BBF compressed the magnetosphere.