Heating of the low-latitude solar wind by dissipation of turbulent magnetic fluctuations

We test a theory presented previously to account for the turbulent transpor t of magnetic fluctuation energy in the solar wind and the related dissipat ion and heating of the ambient ion population. This theory accounts for the injection of magnetic energy through the damping of large-scale flow gradi ents, such as wind shear and compression, and incorporates the injection of magnetic energy due to wave excitation by interstellar pickup ions. The th eory assumes quasi-two-dimensional spectral transport of the fluctuation en ergy and subsequent dissipation that heats the thermal protons. We compare the predictions of this theory with Voyager 2 and Pioneer 11 observations o f magnetic fluctuation energy, magnetic correlation lengths, and ambient pr oton temperatures. Near-Earth Omnitape observations are used to adjust for solar variability, and the possibility that high-latitude effects could mas k possible radial dependences is considered. We find abundant evidence for in situ heating of the protons, which we quantify, and show that the observ ed magnetic energy is consistent with the ion temperatures.