A scale-free analysis of magnetic holes at 1 AU

摘要

We describe a scale-free search for magnetic holes in the solar wind using Wind magnetometer observations between 1994 and 2004. Using magnetic field and ion measurements on the Wind spacecraft, we present the first statistical study of magnetic hole plasma signatures on the kinetic scale and we evaluate magnetic holes as kinetic and fluid phenomena. Magnetic holes are shown to be pressure-balanced structures with similar properties on all scales. Temperature anisotropy measurements are combined with magnetic field measurements to give direct evidence that magnetic holes observed at 1 AU are stable remnants of magnetic pressure depletions generated in a source region closer to the Sun, likely through the mirror-mode instability.