Work

Modeling the EMIC Wave‐Induced Acceleration of Energetic Protons in the Io Footprint Tail

Year: 2026

Type: article

Abstract: The Io footprint tail (FPT) region is crucial for studying the interactions between Io and Jupiter's magnetosphere. In this region, Juno spacecraft observed significant acceleration of energetic protons, concurrently with electromagnetic ion cyclotron (EMIC) waves below the proton gyro‐frequency. Utilizing data from Juno's 12th perijove, we calculate proton scattering rates induced by EMIC waves, and simulate the proton evolution by solving the two‐dimensional Fokker‐Planck equation. Results show that EMIC waves can efficiently accelerate protons from tens of keV to MeV. For ∼50–500 keV protons, the modeled energy spectrum is highly consistent with observations. EMIC waves can largely increase 100 keV proton fluxes by approximately two orders of magnitude within 1 day, a timescale that depends strongly on the wave amplitude. Our results confirm the vital role of EMIC waves in driving proton acceleration in Io FPT, providing essential insights into the global picture of Io‐Jupiter interactions.

Source: Geophysical Research Letters

DOI: 10.1029/2025gl119700