Lognormal and multifractal distributions of the heliospheric magnetic field

The heliospheric magnetic field strength B fluctuates appreciably over a large range of scales in the region from 1 AU to at least 30 AU and throughout the solar cycle. The fluctuations are often extreme and intermittent. For example, the distributions of hour averages of these parameters are usually lognormal to a good approximation, the long tail representing extreme events. The fluctuations can often be described by a multifractal distribution on scales from approximately 12 hours to 27 days or more, reflecting scaling symmetries of various moments of the fluctuations. Statistical variations, burstiness, extreme values, and clusters on various scales are ubiquitous in the time series describing the magnetic field. These properties can be described quantitatively, although not uniquely. Models of the solar wind should at least be consistent with these results. Ultimately, there is a need for physical models that can explain the statistical properties of the observed large-scale fluctuations.