Evidence of magnetic field line merging in the solar wind

An analysis is presented of a few of the sector boundary crossings measured by the Pioneer 8 magnetometer. By using a variance matrix technique, evidence is obtained of some amount of magnetic line reconnection through the sector boundaries. The thicknesses of such structures are around 0.1–2 × 104 km and are therefore larger than typical ion Larmor radii, in contrast with the magnetic structures characteristic of the geomagnetic tail. A theoretical discussion is given of the possible physical causes of the observed reconnection process. In particular, the possible role of tearing instabilities is analyzed with reference to the results of the observations.