A Permutation Entropy Analysis of Voyager Interplanetary Magnetic Field Observations

Abstract

AbstractThe permutation entropy analysis technique is here employed to study Voyager 2 observations of heliospheric field fluctuations from ∼6 AU to ∼34 AU for the first time. The properties of the technique, especially regarding the classification of a given process as either chaotic or stochastic, are illustrated in some detail and it is indicated how the technique is best applied and interpreted to the data set in question. Proceeding from this, conclusions are made regarding the stochasticity of the processes driving turbulence as a function of radial distance from the Sun, which is here found to increase with distance toward a value theoretically associated with Brownian motion, exceeding that value depending on the data bin size considered. At larger radial distances, however, it is argued that this trend may be influenced by a strongly declining signal‐to‐noise ratio. Intriguingly, this technique also serves to identify intervals of anomalously moderate to low stochasticity, which are briefly investigated here.