Abstract: Up to now, the equatorial counter electrojet (CEJ) is considered as an unusual phenomenon, which is caused by a special combina-tion of tidal modes, or by a local vertical wind shear or a gravity-wave at ionospheric height above the equator. This paper shows, however, under an average state given by the empirical models of IRI-90, MSIS-90 and HWM-90 for middle-and low-latitude ionospheres on geomagneticallyquiet days, the CEJ occurs frequently. On the other hand, the CEJ disappears under the effect of the electrostatic potentialacross the polar cap (the dawn-dusk electic field) driven by the magnetosphere-ionos-phere coupling.

Key words: equatorial electrojet, magnetosphere-ionosphere coupling, electrostatic potential across the polar cap

摘要： 一般认为反向赤道电集流（CEJ）是一种“非”常态现象，其起因可能是潮汐风波模的特殊组合，或赤道上空局地垂直风切或重力波的作用结果。本文表明，在中性大气和水平风经验模式给出的磁静日中低纬平均条件下，CEJ应“正常”地出现。磁层－电离层耦合产生的极盖区边界驱动势（或对流电场）则是CEJ消失的可能机制。

关键词: 赤道电集流, 磁层－电离层耦合, 极盖驱动势