## 4 Discussion
[10] have compared peaks in electron spectrum with the power spectra of geomagnetic data from SAA. They found only statistically insignificant peaks in power spectra of pulsations. They concluded that there is no evidence that an acceleration of high-energy electrons (E \(\sim\) 0.7-1.3 MeV) was caused by the equatorial electrojet variations. [PERSON] et al. [11] have showed that the ionospheric mechanism is not appropriate for the low-energy electrons (E \(<\) 100 keV). In particular, electrons with energy 30 keV have a long period of azimuthal drift of 19.2 h at shells L \(<\) 1.3 (see Figure 2) and, hence, a very long coherence time, of the order of several days, is needed. That is the long drift period of low-energy electrons, indicating that the drift-resonant acceleration mechanism is inappropriate for low-energy electrons. Finally, the ionospheric mechanism is not appropriate for the FEE injections at longitudes far away from the SAA area. Three super storms began with SSC/SI caused by strong compression due to the effects of high solar wind pressure accompanied by south/north Bz IMF. Previous studies [30; 60; 61] reported fast injections of relativistic electrons from the outer ERB to L = 2.5 due to the SSC-associated electric field of 80 mV/m amplitude and of 2 min duration. However, in our study, no FEE enhancements were observed during SSC/SI at L \(<\) 1.2. In contrast, the first FEE in March 2001 occurred 9 h after the SI, in November 2004, 2.5 h after the SSC, and in May 2024, 2 h after the SSC. From Table 1, we can find a tendency in occurrence of the first FEEs at daytime when the solar wind pressure sharply decreases (negative \(\Delta\)P) and at nighttime when the pressure sharply increases (positive \(\Delta\)P). Case studies and statistical data ([4] and references therein) of FEE enhancements have provided reliable confirmation of the mechanism of radial transport from the inner ERB. Additionally, a characteristic feature of the FEE phenomenon is a significant increase in flux by orders of magnitude over a short period of time (tens of minutes). The observations prove that this was a fast transport or injection with a flux growth time shorter than the orbital period of the POES satellites (<1.7 h), which is different from a slow transport or diffusion that takes a few days. In the current study, we found that the first FEE enhancements occurred within a relatively short time (<20 min) after the pressure change affected the magnetosphere. In addition, the shortest time of the injection of 10 min was estimated for the case of 10 May 2024 based on the successive passes of two satellites. Thus, we conclude that even 10 min may be sufficient for injection into the lower L-shells during periods of great storms. We now compare this observed time with simplified theoretical estimations derived for the electric drift. The characteristic time of electric drift \(T\) across \(L\)-shells over a distance \(\delta L\) with velocity \(V_{DE}\) is expressed by the relation [8]:  
\[T=a\cdot\delta L/V_{DE}, \tag{4}\]  
where the Earth's radius a = 6380 km, and \(V_{DE}\) is the electric drift velocity. In the dipole field approximation and in the equatorial plane, there is a simple expression for the velocity: \(V_{DE}=E_{\perp}/B\)[18]. Moving on to the non-systemic units generally accepted in space physics [km/s, mV/m, nT], we obtain the formula for \(V_{DE}\) in [km/s]:  
\[V_{DE}=0.032\cdot L^{3}\cdot E_{\perp} \tag{5}\]  
Then we perform integration (4) over \(L\) in the interval [\(L_{0}\); \(L_{1}\)]:  
\[T=a\cdot\int\limits_{L_{0}}^{L_{1}}\frac{dL}{V_{DE}},\]  
and we obtain an expression for the characteristic drift time T(\(E_{\perp}\), L\({}_{1}\)) in minutes:  
\[T=\frac{1.66\cdot 10^{3}}{E_{\perp}}\cdot[L_{1}^{-2}-L_{0}^{-2}] \tag{6}\]  
Figure 7 shows the dependence of \(T\) on \(L\)-shell for different electric field magnitudes \(E_{\perp}\).