Power spectra and discontinuities of the interplanetary magnetic field - Mariner 4.

Power spectra from 3 × 10−4 to 0.5 cps based on Mariner 4 interplanetary magnetic field data show a dependence on frequency ƒ that is roughly of the form ƒ−γ with γ typically near 3/2 and essentially always between 1 and 2 for each of the three components and for the absolute value of the field. This is based on the analysis of data for days of widely ranging degrees of activity near solar minimum. Power levels were typically a factor of 10 higher for disturbed than for quiet days and, except on quiet days, were a factor of 2 higher for the various components than for the absolute value. Data relating to frequently occurring field discontinuities show few shocks and many contact surfaces. The associated current sheets are found to be unusually thin, roughly 50% of those analyzed had thicknesses less than 3500 km and 10% less than 500 km. The structure of the current sheets that produced the cleanest discontinuities was analyzed and shown to be consistent with that of a tangential discontinuity characterized by zero normal field and normal velocity components. The directional distribution of current sheet normals strongly suggests a local latitudinal solar wind shear that prevails over one sector and can change from sector to sector. The cross sections of magnetic filaments are found to be in some cases highly elliptical rather than more-or-less circular, again suggesting a latitudinal solar wind shear.

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