The Role of Dust in Creating Magnetic Turbulence in the Solar Wind

Dust is produced in the solar system by cometary outgassing and by collisions. This dust becomes immediately ionized and subject to the solar wind electric field. A rare but highly recognizable signature can be found in thin intense current sheets seen within ICMEs, the largest magnetic constructs in the solar system. These have been attributed to the ICME passage through comet tails. We present new examples in this talk. A second source of fine-scale dust manifests itself in the undisturbed solar wind when meteoroids collide, producing dust clouds that are then accelerated to the solar wind speed. Until the magnetized dust cloud reaches the solar wind speed, a magnetic pressure enhancement exists that transfers momentum from the solar wind to the charged dust. Since the ions and the charged dust have very different gyroradii and drift paths, a strong current sheet is formed between the ion-dominated plasma and the charged dust plasma. When the magnetic enhancement disappears, the magnetic cloud is no longer identifiable. However, the current sheet continues to be carried outward by the solar wind. If the charged-dust containing cloud later crosses the Earth's bow shock, the magnetized charged dust cloud continues to rush through the magnetosheath until it reaches the magnetopause where it develops a magnetic pressure 'cap' that slows it down. This feature is clearly seen in MMS records associated with current sheets. Those current sheets produced by the deceleration of the dust cloud in the magnetosheath are among the strongest currents observed by MMS. These solar wind and magnetosheath current sheets are the source of at least part of the turbulent structure of the interplanetary and magnetosheath magnetic fields, especially the turbulence seen outside stream-interaction regions.