Interplanetary Magnetic Field Curvature and Its Role in Particle Acceleration: Magnetospheric Multiscale and Solar Orbiter Observations

Abstract The curvature of the magnetic field plays a crucial role in magnetic confinement, magnetic reconnection, particle heating, and acceleration. Though the magnetic field curvature has been sufficiently investigated in the terrestrial magnetosheath, there is a lack of research in the more extensive interplanetary space. This study, combining the Magnetospheric Multiscale and Solar Orbiter (SolO) observations, investigates the magnetic field curvature in the near-Earth and interplanetary space. The spatial distributions and probability distribution functions (PDFs) of the curvature are revealed in the solar wind, magnetosheath, and magnetosphere. It shown that the field curvature in the solar wind follows a two-power-law PDF, similar to that in the magnetosheath but with distinct exponents. We then extend the research to a heliocentric distance of [0.3, 1.0] au, with the aid of an indirect estimation method of magnetic field curvature that can be applied to the SolO data. The average curvature, as a function of heliocentric distance, exhibits a U-shape variation with the minimum curvature appearing at 0.5 au. A possible explanation for such a variation is also given and supported by the spacecraft data. This work could improve our understanding of the turbulent environment in the interplanetary space and demonstrate the universality of a recently proposed acceleration scenario of electrons due to the interaction of shocks and curved magnetic field lines.