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The choice of interval of averaging in computing statistics of solar wind fluctuations is known to be a sensitive issue in which the need for adequate sampling statistics must be balanced with the complications of establishing an ensemble, given that the solar wind admits inhomogeneity, structure, and variability at its sources. Here we examine the quantitative dependence of interval of averaging (sample size) on estimates of basic statistics such as means, variances, and anisotropies of the measured interplanetary magnetic field.

Recent observational studies show strong statistical associations between features of interplanetary suprathermal energetic particle (EP) data and rapid changes in the interplanetary vector magnetic field. The latter are connected to intermittency and coherent magnetic structures, including classical discontinuities. Here we discuss these observations in the context of two appealing theoretical ideas: First, magnetic structures bounding flux tubes can cause local or temporary topological trapping, thus influencing EP transport. Second, charged particles may be accelerated by interacting with dynamic flux tubes, either through reconnection, trapping in secondary islands, or a betatron mechanism. We present observations that support interpretation in terms of trapping boundaries associated with changes in EP flux and also find a case in which an EP peak lies near a coherent magnetic structure that is not a shock, with changing particle anisotropy consistent with outflow from the structure, suggestive of local particle acceleration.

[1] We examine five corotating interaction regions and their surrounding slow and fast wind flows observed by the Advanced Composition Explorer spacecraft at 1 AU during solar minimum conditions in 2007 and 2008. We compute spectra of total power (magnetic + kinetic) and spectra of the cross helicity in an attempt to better understand turbulence generation within the shear flow. Consistent with previous work, we find that Sunwardpropagation signatures exist at high levels compared with the surrounding flow and sometimes dominate over a broad range of spacecraft-frame frequencies. There is a suggestion that the Sunward-propagation signatures start at small scales and evolve toward larger scales, although this may simply reflect the need to inject larger amounts of energy at the large scales before significant Sunward propagation is observed. The power spectra are conspicuously lacking in any features that would normally be expected to show energy injection over a finite range of frequencies as is the often the case in kinetic instabilities.