Micro-scale structures in the interplanetary medium

This report describes and analyses the following micro-scale (.01 AU) structures which were found in combined interplanetary magnetic field and plasma data obtained by the deep-space probe, Pioneer-6: (1) Several types of simultaneous discontinuities in the magnetic field and plasma parameters; (2) at least one clear example of a transitional region (D-sheet) associated with a plasma discontinuity; (3) other D-sheets which give evidence of magnetic-field annihilation; (4) inhomogeneous isothermal regions in which the square of the magnetic-field intensity is proportional to the density; (5) periodic variations in the magnetic-field intensity which are associated with discontinuities in the bulk speed. It is suggested that small velocity discontinuities play a fundamental role in reducing stresses in the interplanetary medium, and that large-velocity discontinuities may give rise to waves and turbulence.NAS-NRC Postdoctoral Resident Research Associate.