2019/12/05 by C. H. K. Chen, S. D. Bale, J. W. Bonnell +22 · 7 citations
Physics and Astronomy · #Energy flux #Heliosphere #Interplanetary magnetic field #Ionosphere and magnetosphere dynamics #Kinetic energy #Magnetohydrodynamic turbulence #Magnetopause #Solar and Space Plasma Dynamics #Solar wind #Stellar, planetary, and galactic studies #Turbulence #Turbulence kinetic energy #astro-ph.SR #physics.plasm-ph #physics.space-ph
paper · pdf · doi:10.3847/1538-4365/ab60a3
arxiv created 2019/12/05 · openalex created_date 2019/12/13 · openalex publication_date 2020/02/01 · arxiv updated 2020/02/04 · openalex updated_date 2026/08/05
Abstract 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.