Observational Evidence for the Modulation of Magnetopause Position by Solar Wind Turbulence

Abstract It has long been known that magnetopause position is primarily controlled by the solar wind dynamic pressure and the interplanetary magnetic field. This classical view, however, largely overlooks the ubiquitous role of solar wind turbulence. Consequently, it remains unclear which turbulent properties most effectively modulate the magnetopause position, on what characteristic scales these effects are most pronounced, and how these turbulence-driven effects are physically mediated. Employing a quasi-controlled-variable approach and excluding dominant disturbances, we perform the first direct statistical investigation by selecting 45 magnetopause crossing events (from 38,018 total between 2007 and 2022) under nearly identical background conditions, isolating the effects of turbulence characterized by its spectral properties, partial variance of increments, and the local energy transfer rate. The analysis, further validated by Cohen’s d effect sizes, reveals that turbulence could modulate the magnetopause position: intervals with flatter plasma spectra in the inertial range, higher incidence of intermittent structures (particularly at ∼47 s), and more intense energy transfer rates (particularly at ∼6 minutes) correlate with a more distant, outward-shifted boundary. These results tend to suggest that highly turbulent solar wind could enhance energy and momentum transfer into the magnetosphere, likely via a combination of viscous-like interactions, localized heating at intermittent structures, and resonant Alfvénic fluctuations, causing the outer magnetosphere to heat and expand. This work provides the first observational quantification of this fundamental coupling, which may offer crucial benchmarks for numerical simulations and new avenues for theoretical research.