## 4 Discussion  
We assume that the energetic electron fluxes below the ERB suddenly enhance due to the solar wind and IMF changes. We investigate the character of these changes to understand the physical principle underlying the FEE enhancement mechanism. This will also allow us to evaluate the key parameters of the mechanism. We apply three criteria to select FEE cases for the analysis. (1) The time interval corresponds to a period when the magnetosphere is strongly disturbed by the impact of a CME, which results in a super storm of about \(-\)500 nT strength. (2) The FEE enhancement should be the first observed by the satellite constellation after the super storm onset. Figure 6: The intensity of flux of the \(>\)30 keV electrons observed by three satellites from 17:00 UT to 21 UT on 10 May 2024. After 19 UT, the satellites crossed the equator in a narrow longitudinal interval (140\({}^{\circ}\) W–150\({}^{\circ}\) W) successively at 19:10, 19:13, and 19:22 UT. MetOp-3 observed an increase in the flux of quasi-trapped electrons at latitudes 10–15\({}^{\circ}\) off the equator. After \(\sim\)10 min, POES-19 observed a large increase in flux at the equator. (3) The simultaneous enhancement in fluxes of electrons with different energies is the main condition for determining the time and location of injection. Suitable cases were found during three super storms and were analyzed in detail. The FEE enhancements occurred during the storm recovery phase on 31 March 2001, at the end of the main phase on 9 November 2004 and at the beginning of the main phase on 10 May 2024 (Table 1). During great storms, the probability of simultaneous increase in electron fluxes in a wide energy range (from tens to low hundreds of keV) is higher [3]. As seen in Table 1, simultaneous enhancements were observed in >30, >100 and >300 keV energy channels during one case and in >30 and >100 keV channels during other two cases. Then we compared the timing of the first FEE enhancements and abrupt changes of the solar wind pressure \(P\) acting on the magnetosphere with a time lag refined from ground-based magnetic observations. Here, we first discuss an important issue concerning the possible influence of SAA electrodynamics and equatorial electrojet on the occurrence of FEE enhancements. The SAA electrodynamics are strongly influenced by energetic particles of the inner ERB precipitating into the atmosphere above the SAA area during geomagnetic storms. [PERSON] and [PERSON] [58] have proposed a mechanism of electric field generation due to presence of conductivity gradients in the E-layer during particle precipitations in the SAA. However, this mechanism can only be applied within the region of SAA or in the vicinity (e.g., [59]). Additionally, sporadic energetic particle precipitations producing abundant ionization cause variations of the height-integrated conductivity of the ionosphere and modulation of ionospheric currents, in particular, the equatorial electrojet. [PERSON] [9] proposed an ionospheric mechanism of resonant acceleration of energetic electrons of the inner ERB and their radial transport to lower L-shells. The solar wind pressure changes, such as SSC, result in magnetic field fluctuations observed on the ground. As the solar wind drives particle precipitations, variations of the equatorial electrojet are amplified and produce magnetic field oscillations. An alternating electric field with an azimuthal component around the equator is established by solar wind variations. If the period of magnetic fluctuations is about the same as the azimuthal drift period of energetic electrons, then the electrons gain energy during the ionospheric current oscillations. In the ionospheric drift-resonant mechanism, the temporal variations of the equatorial electrojet, flowing at the equator with a width of 400-600 km from the dawn to dusk (to the east), should have the same time scale as the drift period of particles. Hence, the process is selective with respect to energy. [PERSON] et al.