The High-Energy Tail of Energetic Electron Precipitation: Case studies

Precipitating auroral, ring current, and radiation belt electrons will affect the ionization level and composition of the neutral atmosphere. Knowledge gaps remain regarding the frequency, intensity, and the energy spectrum of the Medium Energy Electron (MEE) precipitation (>30 keV). In particular, the understanding and predictive capabilities of the high-energy tail (>300 keV) are in general poor. This study estimates the loss cone electron fluxes from MEPED observations on board the POES/Metop satellites over a full solar cycle 2004-2014 to distinguish >30 keV events from >300 keV events. Data from the Northern and Southern Hemispheres (55-70^oN/S) are combined in daily flux estimates. Flux peaks above the 90th percentile of the >30 kev flux are identified. The 33% highest and lowest associated responses in the >300 keV fluxes are labeled "E3 events" and "E1 events", respectively, resulting in 55 events of each type. Based on superposed epoch analysis, it is evident that high geomagnetic activity increases the probability of E3 events. More specifically, elevated solar wind speeds persisting in the recovery phase of a deep Dst trough appear characteristic of E3 events. Here, we test this assessment by examining solar wind parameters and geomagnetic indices for a selection of single events:

• E1 and E3 events with similar >30 keV flux strengths
• The E1 event with highest >30 keV flux strength
• The E3 event with the weakest >30 keV flux strength
• The E1 event with the strongest Dst deflection
• The E3 event with the weakest Dst deflection