## 5 Conclusions  
This study reports the temporal and spatial distributions of ELF/VLF wave activities and energetic particle enhancement in the mid-high latitude ionosphere during storm time based on observations from the SCM, EFD, and HEPP-L payloads onboard the CSES, which has been operating in low Earth orbit at an altitude of 507 km from February 2018 to present. The 26 August 2018 intense storm resulted from an ICME event from the Sun, leading to strong ELF/VLF emissions and energetic electron precipitations in the upper ionosphere. Figure 12: The wave propagation parameters computed by the singular value decomposition (SVD) method for the ELF/VLF waves in the high-latitude ionosphere during the geomagnetic storm recorded by orbit No. 0031290 on 27 August 2018. From top to bottom: the sum of the PSD values of the three components of the magnetic field (**a**) and the electric field (**b**); the ellipticity (**c**); the wave normal angle (**d**) and the azimuthal angle (**e**) for wave vector k; and the planarity (**f**) and the perpendicular and parallel component of the Poynting vector (\(S_{\perp},S_{\parallel}\)) (**g.h**). The superposed epoch analysis for ELF/VLF waves and particles indicated that before the ICME hit the magnetopause, the wave activities and particle precipitation were relatively weak in the ionosphere, and the climax of wave excitations mainly appeared during the near-end main phase and the early recovery phase. Regarding frequency, the waves at frequencies below 6 kHz mainly occurred at the early stage of the main phase; a broad frequency band wave from \(f_{\rm cp}\) to 20 kHz was remarkably excited from the near-end main phase to the early recovery phase. During the long period of the recovery phase, the wave enhancements mainly occurred below 6 kHz. The wave activity in the nightside ionosphere showed a good correlation with the evolution of the geomagnetic storm, but the amplitude of such was weaker than that on the dayside its spatial scale was also narrowly distributed. The energetic precipitating fluxes increased with geomagnetic activity and reached their maximum during the early recovery phase, as primarily observed outside of the plasmapause. The energetic electrons at an energy level below 1.5 MeV got strong enhancements during the entire storm time on both the day and night side (relatively stronger than the ones on the dayside), and they also appeared both inside and outside the plasmapause; for particles \(E>1.5\) MeV, the fluxes mainly got enhancement from outside the plasmapause. An investigation into a large amount of half orbit data in the whole time period showed that under the quiet condition, the CSES depicted the outer/inner radiation belt in the slot region well, whereas under disturbed conditions, such regions were invisible and dominated by precipitations of \(E<1\) MeV all along the CSES orbit space. The regions poleward from the geomagnetic latitude of 50\({}^{\circ}\) corresponded to the highest electron precipitation regardless of the quiet or active conditions; the regions equatorward below 30\({}^{\circ}\) were usually enhanced during the storm time and occasionally during the quiet time. The ELF/VLF waves recorded by the CSES during the storm time mainly included structure-less VLF waves, structured ELF/VLF quasi-periodic emissions, and non-structured ELF has waves. A wave vector analysis indicated that the ELF/VLF waves were right-handed polarized whistler-mode waves, and they obliquely propagated from some area higher than the satellite (most likely from the outer radiation belt) to the Earth direction. Conceptualization, Z.Z. (Zeren Zhima); data curation, Y.H., W.C., M.P., A.P., Z.Z. (Zhenxia Zhang), Q.W., J.H., S.Z., Y.Y., D.Y., X.S. (Giaoying Sun), Q.T., N.Z., and F.G.; formal analysis, Z.Z. ([PERSON]), W.C., M.P., A.P., and Z.Z. ([PERSON]); funding acquisition, Z.Z. ([PERSON]); investigation, Z.Z. (Zeren Zhima), Y.H., W.C., M.P., A.P., Z.Z. (Zhenxia Zhang), Q.W., J.H., S.Z., Y.Y., D.Y., and X.S. (Giaoying Sun); methodology, Z.Z.