ULF Waves Associated with Periodical High Speed Flows in the Magnetotail Plasma Sheet

Abstract

In this paper, using the data of Cluster satellites on 8 November 2004, we analyze the ULF waves associated with earthward periodical high speed flows in the magnetotail plasma sheet. The results show that the ULF waves in the magnetic field and temperature appear, enhance and end at the same times with those of periodical high speed ion flows. Particularly, the oscillation frequencies in the ion flow velocity and magnetic field are both between 60 70 mHz, i.e. in the frequency range of Pi1. These observations suggest that the ULF waves in the magnetic field and ion temperature are highly correlated with the periodical high speed flow. The oscillation of the high speed flow is approximately out of phase with the ULF wave in the magnetic field and in phase with that in ion temperature. The result of minimum variance analysis shows that although the wave propagation direction includes an earthward component, the major propagation direction is towards the centre of the plasm!

a sheet and perpendicular to both the high speed flow velocity and magnetic field. All these observations indicate that periodical high speed flows can generate ULF waves in the Pi1 frequency range.