Oscillatory magnetic flux tube slippage in the plasma sheet
Cluster observations in the magnetotail revealed an abundance of strongly inclined current sheets. We determine the magnetic configuration of a particular subset of such phenomena: a series of sheet crossings, having significantly differing inclinations and occurring during quiet conditions. These wave-like variations appear to propagate azimuthally and their magnetic amplitude and magnetic gradient (current density) inside the sheet are proportional to their steepness (degree of inlcination). In spite of significant normal direction changes between neighboring crossings up to 150°, the magnetic field direction inside the neutral sheet remains almost constant. The wavelengths and spatial amplitudes are of the order of 2–5 RE. These observations are interpreted as crossings of a quasi-periodic dynamical structure produced by almost vertical slippage motion of the neighboring magnetic flux tubes in the high-β plasma sheet, rather than large-scale flapping of a stationary structure.