THE RATE OF TURBULENT EVOLUTION OVER THE SUNS POLES

Ulysses magnetic field observations in the polar heliosphere have reve aled the presence of a population of turbulent fluctuations on small s cales with a power spectral index near 5/3 and its extension to progre ssively larger scales with solar distance. Using the spectral index - calculated from the second order structure function - as a tracer of t he turbulent nature of the fluctuations, the rate of extension of the turbulent regime with distance is measured for both the Northern and S outhern polar heliosphere. The evolution is similar in both hemisphere s: the exponent of the rate of extension of the turbulent regime with solar distance is + 1.1 +/- 0.1. By comparing of the extent of the tur bulent regime in the polar heliosphere with previous measurements of f luctuations near the ecliptic, polar fluctuations are shown to evolve more slowly than those in high speed streams at lower heliolatitudes b eyond 0.3 Astronomical Units. Within this distance, however, fluctuati ons in high speed streams at high and low latitudes probably evolve at the same rate.