CLUSTER OBSERVATIONS OF THE FIELD AND PLASMA STRUCTURE OF CURRENT SHEETS IN THE SOLAR WIND

摘要

When the apogee of the Cluster spacecraft is on the day-side between mid-January and mid-April each year, the 4 spacecraft spend several hours per orbit upstream of the bow shock, and thus sample the fields and plasmas of the solar wind. The multi-point nature of the mission allows unambiguous determination of many properties of structures convecting with the solar wind. For example, 4 spacecraft timing analysis can be used to determine the orientation and thickness of 2D structures embedded in the solar wind, while the 'curlometer' technique can be used to determine the associated electric current density. We present analyses of Cluster data from 2 crossings of current sheets in the solar wind. We find that in common with current sheets observed within the magnetotail, the current may show a bifurcated structure. In addition, intense, narrow current sheets may be embedded within broader current structures. We also examine the ion and electron distributions within and around these sheets in order to determine how the currents are supported.