Using the high resolution field and plasma data obtained from the Magnetospheric Multiscale mission(MMS)at the magnetopause,a series of three flux transfer events was observed inside southward ion flows.Using the plasma measurements,the current densities within the flux ropes were studied in detail.The current within the first two flux ropes,dubbed Fr1and Fr2,was composed of a series of the well-separated filamentary currents.The thickness of the filamentary currents and the gap between them were sub-ion scale,occasionally dropped down to electron-scale.In the third flux rope Fr3which was closest to the expected reconnection X-line,the current displayed a singular compact current layer.Considering the location of the flux ropes relative to the reconnection X-line,we suggested the current density could be a singular structure when the flux rope was just created and then fragmented into a series of filamentary currents as time.By examining the inter-regions between Fr1and Fr2,and between Fr2and Fr3,reconnection was only confirmed to occur between Fr2and Fr3and no reconnection signature was found between Fr1and Fr2.It seems that the compression of the local magnetic field between two neighboring flux ropes is one necessary condition for the occurrence of the coalescence.
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