Flux tube texture of the solar wind: Strands of the magnetic carpet at 1 AU

摘要

It is argued here that the inner heliosphere is filled with a network of entangled magnetic flux tubes and that the flux tubes are fossil structures that originate at the solar surface. 65,860 flux tubes are collected from seven years of measurements with the ACE spacecraft at 1 AU by spotting the flux tube walls with large changes in the magnetic field direction and the vector flow velocity. The tube walls are associated with large changes in the ion entropy density and the alpha-to-proton ratio. The median size of the flux tubes at 1 AU is 4.4 × 105 km. The tubes are larger in slow wind than in fast wind. The tubes are on-average aligned with the Parker spiral, with a large spread in orientations. This large spread may be caused by slight misalignments of tubes in the corona. The flux tubes map to granule and supergranule sizes on the Sun. The amounts of magnetic flux in the tubes at 1 AU correspond to the amounts of magnetic flux in field concentrations in the magnetic carpet. It is argued that the flux tubes do not reconnect during the ～100-h advection to 1 AU owing to the expansion of the solar wind. The flux tube texture impacts the flow properties of the solar wind, turbulence in the solar wind, energetic-particle propagation in the inner heliosphere, and the driving of the Earth's magnetosphere. A method for using measurements of the flux tube walls for the remote sensing of magnetic field dynamics in the magnetic carpet is suggested.