Intermittent Heating in the Magnetic Cloud Sheath Regions

Coherent structures such as current sheets have been usually regarded to be sites of proton heating in the solar wind. In this Letter, we statistically investigate the proton heating effects around the coherent structures within the turbulent sheath regions of magnetic clouds (MCs) based on WIND observations. It is found that the proton temperature enhancement near coherent structures in the MC sheath is not as remarkable as in the solar wind. Significant temperature increase only exists near coherent structures with great directional changes (>45°) in magnetic field or intensity changes (≥10% of the mean magnetic field magnitude), which merely account for 13% of the total of 12,426 identified intermittent events in the 71 studied MC sheaths. The temperature increment is more evident near strong current sheets with great directional changes (>45°) at smaller scales than those at larger scales. It suggests that the heating effects in the MC sheath regions are likely to be highly localized. The local proton heating effects in the turbulent sheath are probably caused by the magnetic reconnection processes that are frequently associated with the strong current sheets.