Researchers frequently use high-power large aperture (HPLA) incoherent scatter radar (ISR) instruments around the world to gather data about meteoroids entering Earth's atmosphere. HPLA radar instruments measure between hundreds and thousands of head echoes per hour, depending on factors including frequency, power, geographic location and beam direction, in addition to the observed meteor population, that influence head echo detectability. High detection rates enable the use of statistical methods for head echo populations. The observed head echoes often originate from particles that are tens of microns in diameter; larger than the particles that can be observed in situ via impact detectors (Baggaley et al., 2007), but smaller than those observed via optical methods (Brown et al., 2017;Campbell-Brown & Close, 2007). Furthermore, signal processing techniques can be leveraged to obtain extremely accurate measurements of meteor motion during atmospheric entry from radar data.As a meteoroid ablates in Earth's atmosphere, a plasma forms at altitudes from 80 to 130 km due to sputtering and thermal ablation upon high-velocity collisions between the meteoroid and atmospheric molecules (Guttormsen et al., 2020;Popova et al., 2001). The high-density plasma cap that surrounds the meteoroid reflects radio waves, producing the head echo radar signature. Head echoes are observable at any HPLA radar. As the plasma expands and undergoes collisions with the surrounding atmosphere, a Farley-Buneman gradient-drift instability may develop in the meteor trail and create a non-specular radar return (Oppenheim & Dimant, 2015;Oppenheim et al., 2000). Most trails occur at equatorial radars due to field-aligned-irregularity (FAI) scattering when the incident wave is perpendicular to the background magnetic field (L. P. Dyrud et al., 2005), although non-FAI scattering has also been observed at higher latitudes (Chau et al., 2014;Kozlovsky et al., 2020).As the meteoroid heats and ablates, differential ablation may occur where certain constituents thermalize before others. This can create variation in radar cross-section during head echo detection, and such variation at the Arecibo radar facility was demonstrated to match the results of an ablation model (L. Dyrud & Janches, 2008;Janches et al., 2009). The effect has been observed in the laboratory for submicron-scale particles (DeLuca et al., 2022). The process of differential ablation may cause the meteoroid to fragment during atmospheric entry. Fragmentation has been observed optically (Vida et al., 2021), and on radar instruments via polarization of the

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Energetic Particle Precipitation (EPP) represents one of the major sink (or loss) processes for outer radiation belt electrons (e.g., Crew et al., 2016;Thorne, 2010). Other loss processes include outward radial diffusion to the magnetopause and loss of adiabaticity on stretched magnetic field lines (Crew et al., 2016;Ukhorskiy, 2006), a phenomenon referred to as magnetopause shadowing. For EPP, despite the observed presence of coterminous waves with certain types of precipitation, it is remarkably difficult to verify directly that those waves are in fact responsible for such precipitation (Kaeppler et al., 2020). In this work we focus on EPP and their space and ground detection.Once precipitated, the energy transferred during collisions between precipitating particles and neutral components of the atmosphere can ionize and dissociate the collision components, and can lead to chain reactions that considerably disrupt the chemical properties of the upper atmosphere (e.g.,