Magnetic field signatures of unevolved turbulence in solar polar flows

Abstract

Between late 1993 and the middle of 1994, Ulysses stayed almost constantly within flows from the Sun's southern polar coronal hole, traveling from 44°S to 69°S heliolatitude and between 4.0 and 2.9 AU from the Sun. Magnetic field observations within this region reveal a very different medium from that at similar heliocentric distances near the ecliptic. Nearly 160 days of magnetic field data taken within this region are studied using structure functions. We demonstrate that the polar plasma flow is turbulent, with different populations of fluctuations on different scales. On spacecraft scales of 102–103 s, the fluctuations are indicative of inertial range turbulence and are intermittent, with a spectral slope near 1.7. On larger scales, the fluctuations are not intermittent, and the spectral slope is near 1. The similarities and differences between polar and near‐ecliptic fluctuations are discussed.