The Distribution of the Ionospheric Conductivity, the Morphology of the Convection Reversal and the Feature of Birkeland Currents (Model Analysis)

The effect of the distribution of ionospheric conductivity and the morphology of the convection reversal on the feature of Birkeland currents is discussed by means of simple models.It is shown: the region 1 field-aligned current is the basic one and connected closely by with the convection reversal;the region 2 field-aligned current,on the other hand,is caused by the shielding of the convection field,or by the decrease of the ionospheric conductivity.The variation of the ionospheric conductivity can also cause the production of the so-called zero region field-aligned current poleward to the region 1 current,and the reverse current equator-ward to the region 2 current.The analysis also demonstrates that the current distribution connected with the rotation reversal is different from that connected with the shear reversal.The paper presented may contribute a little understanding of the complex feature of Birkeland current.It may also interpret the different distribution of field-aligned currents under same condition of the interplanetary magnetic field.