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  • The Evolution and Role of S...
    Chen, C. H. K.; Bale, S. D.; Bonnell, J. W.; Borovikov, D.; Bowen, T. A.; Burgess, D.; Case, A. W.; Chandran, B. D. G.; de Wit, T. Dudok; Goetz, K.; Harvey, P. R.; Kasper, J. C.; Klein, K. G.; Korreck, K. E.; Larson, D.; Livi, R.; MacDowall, R. J.; Malaspina, D. M.; Mallet, A.; McManus, M. D.; Moncuquet, M.; Pulupa, M.; Stevens, M. L.; Whittlesey, P.

    The Astrophysical journal. Supplement series, 02/2020, Letnik: 246, Številka: 2
    Journal Article

    The first two orbits of the Parker Solar Probe spacecraft have enabled the first in situ measurements of the solar wind down to a heliocentric distance of 0.17 au (or 36 ). Here, we present an analysis of this data to study solar wind turbulence at 0.17 au and its evolution out to 1 au. While many features remain similar, key differences at 0.17 au include increased turbulence energy levels by more than an order of magnitude, a magnetic field spectral index of −3/2 matching that of the velocity and both Elsasser fields, a lower magnetic compressibility consistent with a smaller slow-mode kinetic energy fraction, and a much smaller outer scale that has had time for substantial nonlinear processing. There is also an overall increase in the dominance of outward-propagating Alfvénic fluctuations compared to inward-propagating ones, and the radial variation of the inward component is consistent with its generation by reflection from the large-scale gradient in Alfvén speed. The energy flux in this turbulence at 0.17 au was found to be ∼10% of that in the bulk solar wind kinetic energy, becoming ∼40% when extrapolated to the Alfvén point, and both the fraction and rate of increase of this flux toward the Sun are consistent with turbulence-driven models in which the solar wind is powered by this flux.