Heliospheric magnetic field polarity inversions driven by radial velocity field structures

Magnetic field polarity inversions embedded in the predominantly unipolar fast solar wind have been observed by the Ulysses spacecraft at high latitudes. Such reversals have the nature of folded back field lines which we suggest are generated by the interaction of standard large amplitude, low frequency, Alfve ́nic turbulence with velocity shears in the fast solar wind. We present 2D magnetohydrodynamic simulations of a very low frequency and high amplitude Alfve ́n wave propagating away from the sun embedded in a velocity shear structure such as a microstream and show how reversals in the magnetic field lines are generated naturally on a time-scale consistent with their observation at Ulysses. The generated magnetic field and plasma signals are similar to those observed. We discuss the role turbulence-stream shear interactions might play in limiting differential velocities in the asymptotic high speed solar wind.