Statistical Characteristics of Electron Precipitation During HSS‐ and ICME‐Driven Storms Observed by the EISCAT Radar

Abstract The 1–100 keV electron precipitation during storm time has been studied by applying the updated ELSPEC inversion method to field‐aligned electron density profiles measured by the EISCAT Tromsø radar at L = 6.5. The statistical properties of peak energy, total energy flux, and total number flux as a function of MLT have been studied for the two main solar wind drivers (high‐speed streams, HSSs, and interplanetary coronal mass ejections, ICMEs), and two storm phases (main and recovery) between 1998 and 2023. We found that the peak energy grows after midnight until noon, but the number fluxes behave in the opposite manner, decreasing toward noon. Electron precipitation in this region is believed to be caused by lower‐band chorus waves. The peak energies were lower for ICME‐driven storms than HSS‐driven storms. At 10–12 MLT, the maximum in the mean peak energy was 43 keV for HSS‐driven storms and 28 keV for ICME‐driven storms. The probable reason is the change in the equatorial magnetic field value during storms affecting resonant energies of electrons. ICME‐driven storms were stronger in magnitude than HSS‐driven storms, and hence the equatorial magnetic field at L = 6.5 decreased more for ICME‐driven storms. The same mechanism can explain why the peak energies in the pre‐noon sector during the main phase were lower than during the recovery phase. The number fluxes and energy fluxes were larger in the main phase than in the recovery phase in the morning sector.