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Abstract We recently reported the finding of elementary rising‐tone emissions embedded within each harmonic of magnetosonic waves, by investigating wave electric field waveforms measured by Van Allen Probes. The present study further uncovers a new set of fine structures of magnetosonic waves, namely, each elementary rising‐tone may consist of a series of mini harmonics spaced around the O⁺gyrofrequency. The measured ion distributions suggest that the proton ring distribution provides free energy to excite the waves, whilst the O⁺ions suppress the wave growth around multiples of O⁺gyrofrequency, resulting in the formation of mini harmonics. Further investigation suggests that the warm plasma dispersion relation, that is, the ion Bernstein mode instabilities, may contribute to the formation of mini harmonics. The mini harmonic structure implies a new mechanism of energy redistribution among ion species in space plasmas, potentially providing a new acceleration mechanism for O⁺ions in the magnetosphere. 

Abstract Solar Energetic Particles (SEPs) are present during increased solar activity, often associated with solar flares and coronal mass ejections (CMEs). Measuring and understanding these particles is important both for fundamental solar physics knowledge as well as the determination of radiation risks in interplanetary space. Solid‐state particle telescopes are a useful tool to measure these particles. The Relativistic Electron and Proton Telescope integrated little experiment‐2 (REPTile‐2) was a solid‐state energetic particle telescope that flew onboard the Colorado Inner Radiation Belt Experiment (CIRBE) and demonstrated a capability to measure electrons from 0.25 to 6 MeV and protons from 7 to 100 MeV with high energy and time resolution. REPTile‐2 operated in a low‐Earth orbit (LEO) and primarily measured radiation belt particles but was also able to measure SEPs during high‐latitude passes. Because of REPTile‐2's solid performance and its CubeSat‐scale size, weight, and power, an opportunity arose to fly a modified REPTile‐2, dubbed REPTile‐3, on the Emirates Mission to the Asteroid Belt (EMA). In this paper, Geometry and tracking 4 (Geant4) Monte Carlo simulations are used to motivate changes to improve REPTile‐3's ability to measure SEPs. Additionally, full instrument response functions and estimated count rates are used to understand the instrument's response to SEP fluxes. REPTile‐3 is shown to be able to measure 1.2–35 MeV protons with ΔE/E < 9%, 35–100 MeV protons with ΔE/E < 50%, 0.1–5 MeV electrons with ΔE/E < 14%, 18–131 MeV helium ions with ΔE/E < 7%, and 131–200 MeV helium ions with ΔE/E < 50% with a 102° field of view (FOV). 

Abstract Following the largest magnetic storm in 20 years (10 May 2024), REPTile‐2 on NASA's CIRBE satellite identified two new radiation belts containing 1.3–5 MeV electrons aroundL = 2.5–3.5 and 6.8–20 MeV protons aroundL = 2. The region aroundL = 2.5–3.5 is usually devoid of relativistic electrons due to wave‐particle interactions that scatter them into the atmosphere. However, these 1.3–5 MeV electrons in this new belt seemed unaffected until a magnetic storm on 28 June 2024, perturbed the region. The long‐lasting nature of this new electron belt has physical implications for the dependence of electron wave‐particle interactions on energy, plasma density, and magnetic field strength. The enhancement of protons aroundL = 2 exceeded an order of magnitude between 6.8 and 15 MeV forming a distinct new proton belt that appears even more stable. CIRBE, after a year of successful operation, malfunctioned 25 days before the super storm but returned to functionality 1 month after the storm, enabling these discoveries.