The field-aligned currents effect on equatorial geomagnetic field variations Original Research Article

Variations of the H-component of the geomagnetic field at equator are investigated. It is shown that the part of the geomagnetic field variations at equator can be associated with auroral electric fields. The counterelectrojet events (CEJ) and the strengthening of equatorial electrojet (EEJ) can attribute to the electric fields from the field-aligned currents (FAC). It is well known that FAC are controlled by the interplanetary magnetic fields (IMF) and electric fields from the FAC can direct penetrate to equatorial ionosphere. The additional increases of the H-component at equator are explained by the electric fields of the FAC from Region 1 that can directly penetrate (without regard to the magnetospheric ring current) to the middle-latitude and then to equatorial ionosphere during IMF Bz<0. CEJ events are sttributed to the electric fields of the FAC from Region 2 (IMF Bz>0). Dynamics of the equatorial counterelectrojet (CEJ) in connection with changes of the Bz IMF variations are studied. We show that formation and lifetime of the counterelectrojet events are controlled by the IMF Bz.