Effects of recurrent geomagnetic storms (RGSs) induced by high-speed solar wind streams (HSSs) and corotating interaction regions (CIRs) on variations in daytime equatorial electric field (EEF) during 2007-2010 have been investigated. The EEF data as derived from magnetometer data together with the solar wind plasma data reveal many events of striking long duration of oscillating (short-lived) prompt penetration electric fields (PPEFs) about 10-12 hours. The PPEFs exhibited different characteristics depending on the interplanetary origin. The RGSs cause PPEF mainly in the main phase of storms and not all the RGS exhibited penetration of electric field into the ionosphere. Particularly, in some events, PPEF is terminated in the main phase at shock boundary in HSSs.
The turning of magnetic field Bz to the south in the main phase of the magnetic storms are associated not only with the input of energy into the magnetosphere by the magnetic reconnection, but also the PPEF in the day-side equatorial ionosphere by the shielding/overshielding processes. In some events, the northward turning of the IMF Bz is well consistent with quiet time value of the sym-H, which indicates the reduction in the rate of the reconnection.