1.③ The sensonal change of the general ciroution of atmosphere at 50 hPa is mainly drived by the seasonal change oe the temperatu- rs field in the high latitudes which caused by the change from polar dar to polar day to polarnight or from polarnight to polar day.
3.The anomalous FAC pair creates a transient dusk-dawn electric field over the polar cap, tailing behind the original region Ⅰ current and drifting towards the night side until it falls into oblivion.
