The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere

Academic Article

Abstract

  • The first two orbits of the Parker Solar Probe (PSP) spacecraft have enabled the first in situ measurements of the solar wind down to a heliocentric distance of 0.17 au (or 36 Rs). 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 Alfv\'enic 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 Alfv\'en 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 Alfv\'en point, and both the fraction and rate of increase of this flux towards the Sun is consistent with turbulence-driven models in which the solar wind is powered by this flux.
  • Authors

  • Chen, CHK
  • Bale, SD
  • Bonnell, JW
  • Borovikov, D
  • Bowen, TA
  • Burgess, D
  • Case, AW
  • Chandran, Benjamin
  • de Wit, T Dudok
  • Goetz, K
  • Harvey, PR
  • Kasper, JC
  • Klein, KG
  • Korreck, KE
  • Larson, D
  • Livi, R
  • MacDowall, RJ
  • Malaspina, DM
  • Mallet, A
  • McManus, MD
  • Moncuquet, M
  • Pulupa, M
  • Stevens, ML
  • Whittlesey, P
  • Status

    Publication Date

  • February 2020
  • Has Subject Area

    Keywords

  • astro-ph.SR
  • physics.plasm-ph
  • physics.space-ph
  • Digital Object Identifier (doi)

    Start Page

  • 53
  • End Page

  • 53
  • Volume

  • 246
  • Issue

  • 2