Particle acceleration by Magnetic Rayleigh–Taylor instability in the near-Earth magnetotail

High-energy charged particles are ubiquitous in astrophysical, space, and laboratory plasmas, and identifying underlying acceleration mechanisms remains a fundamental challenge. In Earth’s magnetotail, it has been proposed that particles in the mid-magnetotail are initially accelerated to tens to hundreds of keV by magnetic reconnection and subsequently transported to the near-Earth magnetotail, where they are further energized to MeV energies via wave–particle interactions. However, this paradigm hasn’t been verified and particle acceleration processes remain highly controversial. Here, we identify a previously unrecognized acceleration mechanism, dubbed Magnetic Rayleigh–Taylor (MRT) instability, which produces high energy particles up to ~1MeV in the magnetotail. Once the instability is triggered, numerous instability heads characterized by sharp magnetic field enhancements with surrounding flow vortices are generated. As these heads propagate earthward, electron Kelvin–Helmholtz (KH) instabilities are excited and generate super-intense localized electric fields that efficiently accelerates both electrons and ions trapped within the heads. This process results in electron power-law energy spectra with progressively harder indices closer to Earth. These findings demonstrate that the MRT instability is an efficient particle acceleration mechanism in the magnetotail and may significantly contribute to the high-energy particle populations in Earth’s outer radiation belt.