The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere
|Author||Chen, C.; Bale, S.; Bonnell, J.; Borovikov, D.; Bowen, T.; Burgess, D.; Case, A.; Chandran, B.; de Wit, Dudok; Goetz, K.; Harvey, P.; Kasper, J.; Klein, K.; Korreck, K.; Larson, D.; Livi, R.; MacDowall, R.; Malaspina, D.; Mallet, A.; McManus, M.; Moncuquet, M.; Pulupa, M.; Stevens, M.; Whittlesey, P.;|
|Keywords||Astrophysics - Solar and Stellar Astrophysics; Parker Data Used; parker solar probe; Physics - Plasma Physics; Physics - Space Physics; Solar Probe Plus|
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 R\ ⊙\ \ R⊙ ). 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 toward the Sun are consistent with turbulence-driven models in which the solar wind is powered by this flux.
|Year of Publication||2020|
|Journal||The Astrophysical Journal Supplement Series|
|Number of Pages||53|