## 4 Discussion
Hence, this field is approaching very close to the injection region at low L. The question arises of how this field can penetrate into the topside ionosphere at the equator. Figure 7: Time of electric drift from \(L=1.2\) to lower \(L\)-shells, calculated by expression (4) for electric field \(E_{\perp}=5,10,20\) mV/m. We have shown that SSC/SI associated with a large pressure increase does not result in FEE injection. However, the positive pressure pulse during the storm recovery phase is followed by the FEE injection on the night side (see Table 1). When \(\Delta\)P \(>\) 0 acts on the magnetosphere, the magnetic field increases \(\partial B/\partial t>\) 0, in particular in the tail enriched by plasma during the storm main phase. It should be noted that the transient electric field does not relate to the large-scale convection of the plasma flow, which is driven by the south Bz IMF component. At the early recovery phase, a total effect from overshielding and compression might lead to insignificant penetration (i.e., simple shielding) of electric fields of any direction at night. But we infer that if FEE injection occurs at night, then a transient electric field pulse must be of a dawn-to-dusk (westward) direction. It seems that cases with nighttime FEE injections during the recovery phase are not consistent with the penetration convection field concept, whereas the source of transient electric fields is still unknown. The authors of the studies [63; 64] speculated that the subauroral polarization streams (SAPS) may play an important role in deep electron injection at low L shells. They showed that a SAPS electric field has westward direction in the postmidnight-dawn sector. Further, [PERSON] et al. [65] found that the SAPS electric fields penetrate to low latitudes. These studies suggested that the transient westward electric fields resulted from SAPS in the postmidnight sector may be responsible for the radial inward transport of electrons in the inner magnetosphere. In the case of FEE injection, the same question arises about the penetration of transient electric fields to the equator. We further found that the south \(Bz\) IMF component did not directly control the FEE injections. Moreover, the SSC-type compression also does not lead to FEE injections. In these cases, a northward turning of \(Bz\) was observed for \(\sim\)1 h prior to injection. Apparently, the magnetospheric state controlling the \(Bz\) component is important. This means that the \(Bz\) IMF may play a supplementary role in the mechanism of FEE injections. Experimental measurements of electric fields in the inner magnetosphere on the Akebono satellite [33; 34; 35] revealed the presence of transient and highly fluctuated electric fields. The satellite observations showed the transient appearance of pulsed electric fields with strength amplitudes of tens of mV/m in the low L-shells. The strong pulses of the induction electric field occurred with a period of \(\sim\)5-7 min. Other experiments also revealed the presence of inductive electric fields in the plasmasphere and deeper [29; 30; 31; 32]. Electric measurements of the C/NOFS satellite at ionospheric altitudes of 400-900 km [36; 37] showed the presence of alternating electric fields with an azimuthal component oscillation amplitude of E \(\sim\) 5-10 mV/m. Therefore, observations of strong transient (inductive) electric fields in the innermost magnetosphere provide an important argument in favor of the electric drift mechanism, which can explain the rapid (minutes) radial transport of energetic electrons from the inner ERB to the forbidden zone. In our study, we have found a relation between this process and the dynamic pressure of the solar wind.