MMS Observations of Short-Period Current Sheet Flapping

The current sheet kink-like flapping motions are commonly observed in the magnetotail propagating toward the flanks with periods of few minutes down to few seconds with different thicknesses. Here, we report a short period (T≈25 s) flapping event of a thin current sheet observed by the Magnetospheric Multiscale (MMS) mission in the duskside plasmasheet following a dipolarization jet. Using the spatiotemporal derivative and timing methods, we observe that the wavelike structure is propagating along the current density with a phase velocity one order of magnitude less than the ion thermal speed. The presence of a normal electric field and gradients of density associated with lower hybrid waves, suggest an ion scale current sheet which is confirmed by the breaking of the adiabacity condition for ions. We discuss the presence of the lower hybrid waves as a broadening process of the thin current sheet and the scaling of its thickness with the wavelength of the oscillating structure.