Examining Some Properties of the Magnetic and Plasma Structure of the Solar Wind

Abstract:

This analysis focuses on strong current sheets (directional discontinuities), which carry the majority of the magnetic Fourier power of the solar wind. Four properties that seem contrary to active MHD turbulence are examined. (1) In the Alfvenic fast solar wind, the magnetic structure moves en masse through the solar-wind plasma. In the reference frame moving with the structure, the magnetic structure contains proton flows that are everywhere parallel to B. To within measurement error, there is no indication of temporal evolution of magnetic structure. (2) In the slow solar wind, a statistical examination of the “plasma block sizes” finds no evidence for mixing (stretching and folding; homogenization) occurring from 0.3 to 1.0 AU. (3) Compression (or rarefaction) of solar-wind plasma produces an anisotropy of the magnetic structure: there is no indication that the anisotropy recovers with time as one should expect if the structure represented active turbulence. (4) At 1 AU alpha-to-proton ion-composition boundaries are found to coincide with strong current sheets: the composition boundaries can only be created in the corona, not in the solar wind. The accompanying current sheet must be a fossil from the Sun.