Hua et al., 2022 https://doi.org/10.1029/2022GL101096 provided evidence that magnetospheric activity indexes, when integrated over a few-to-several days, can successfully forecast the fluxes in the outer radiation belt (ORB) for relativistic electrons. In this study we expand the investigation of the integration effect on the sub-relativistic range of ORB electrons, with an additional purpose—to look at whether the trapped energetic electron fluxes correlate with the electron density in the nearly-conjugate auroral ionosphere. For this purpose, we analyze THEMIS observations of energetic electron fluxes in the dawn-side magnetosphere at r ~ 6 to 8 Re at energies ~7, 20, 65 and 203 keV, whose precipitation is expected to provide the peak ionization rate at ionospheric altitudes 105, 95, 85 and 75 km, correspondingly. By correlating trapped electron fluxes with the SML index integrated over time intervals of different length (up to 50 h), we confirm that the length of the effective integration time window increases with the energy from 1 to 6 h for 7 and 20 keV to 3–6 days for 203 keV electrons. We demonstrated this progressive energy-dependent time delay using magnetospheric observations combined with simultaneous ionospheric observations of electron density Ne by EISCAT radar in the event study. Statistics confirm the correlation between trapped electron flux and Ne values at corresponding energies/altitudes but also indicate, that at ~200 keV a high trapped flux value requires an additional factor (high concurrent magnetic activity) to provide the intense precipitation.