Relativistic Electron Precipitation Events Driven by Solar Wind Impact on the Earth's Magnetosphere.

Certain forms of solar wind transients contain significant enhancements of dynamic pressure and may effectively drive magnetosphere dynamics, including substorms and storms. An integral element of such driving is the generation of a wide range of electromagnetic waves within the inner magnetosphere, either by compressionally heated plasma or by substorm plasma sheet injections. Consequently, solar wind transient impacts are traditionally associated with energetic electron scattering and losses into the atmosphere by electromagnetic waves. In this study, we show the first direct measurements of two such transient‐driven precipitation events as measured by the low‐altitude Electron Losses and Fields Investigation CubeSats. The first event demonstrates storm‐time generated electromagnetic ion cyclotron waves efficiently precipitating sub‐relativistic and relativistic electrons from >300 keV to 2 MeV at the duskside. The second event demonstrates whistler‐mode waves leading to scattering of electrons from 50 to 700 keV on the dawnside. These observations confirm the importance of solar wind transients in driving energetic electron losses and subsequent dynamics in the ionosphere. Key Points: A corotating interaction region (CIR) and interplanetary coronal mass ejection (ICME), both including interplanetary shocks, are observed resulting in relativistic electron precipitation from low‐altitude orbitDuskside precipitation after CIR impact is driven by intense electromagnetic ion cyclotron waves, showing distinct energy‐L dispersion from magnetic field distortionDawnside precipitation after ICME impact is driven by intense whistler‐mode waves resonating with electrons at high latitudes [ABSTRACT FROM AUTHOR]