Hybrid simulations (kinetic ions, massless fluid electrons) have been performed of the magnetotail current sheet for parameters characteristic of the quiet magnetotail (&ugr;D, bn≪1). Here bn=Bn/B0, &ugr;D=(cEy/Bn)/&ugr;i, Bn is the north/south (z) magnetic field, B0 the asymptotic value of the tailward (x) field and &ugr;i the ion thermal speed, where the magnetospheric coordinate system is used. It is shown that the current sheet is more stable than in previously examined cases with high &ugr;D and/or large bn. A clear single reversal in Bx persists over the entire simulation and a By component is created, with a slow rate of growth (hundreds of &OHgr;-1i, where &OHgr;i=eB0/mic). This is many minutes in real time. It is suggested that the waves are due to an electromagnetic instability of the cross-field ion current. ¿ American Geophysical Union 1994