SH033-05
MHD Turbulence in the Solar Wind: Observations from First Five Encounters of Parker Solar Probe

Friday, 11 December 2020: 19:16
Virtual
Chen Shi1, Marco C M Velli2, Olga Panasenco3, Anna Tenerani4, Jasper S Halekas5, Michael Louis Stevens6, Phyllis L Whittlesey7, Roberto Livi7, Trevor A Bowen8 and Stuart D Bale9, (1)University of California Los Angeles, Earth, Planetary and Space Sciences, Los Angeles, CA, United States, (2)University of California Los Angeles, Los Angeles, CA, United States, (3)Advanced Heliophysics, Pasadena, CA, United States, (4)University of Texas, Austin, TX, United States, (5)University of Iowa, Department of Physics and Astronomy, Iowa City, IA, United States, (6)Smithsonian Astrophysical Observatory, Cambridge, MA, United States, (7)Space Sciences Laboratory, University of California Berkeley, Berkeley, CA, United States, (8)University of California Berkeley, Berkeley, CA, United States, (9)University of California Berkeley, Space Sciences Laboratory, Berkeley, CA, United States
Recorded Presentation
Abstract:
Parker Solar Probe (PSP) has finished its first five orbits, reaching ~28 solar radii to the Sun, much lower than any previous spacecraft. The magnetic field and plasma data collected by PSP provide us with great opportunities to study the properties and evolution of turbulence in the young solar wind. Here, we present a statistical analysis of the PSP data from its first five orbits. We focus on the question that how the MHD turbulence properties vary with different solar wind streams, i.e. fast and slow streams. Our results show that, although the plasma properties, e.g. ion temperature and compressibility, vary significantly with the solar wind speed, the turbulence properties do not have a strong wind-speed dependence. The observed faster radial steepening of magnetic field power spectrum in the slow wind indicates that the “age” of the turbulence, determined by the wind speed together with the radial distance, controls the turbulence properties. We observe that as we get closer to the Sun, the spectral slopes of the magnetic field and velocity tend to converge to a value ~1.5 and the residual energy rises from negative values toward 0. This result confirms that the observed asymmetry between kinetic and magnetic energies and power spectra beyond 0.3 AU is a result of dynamic evolution of the turbulence.
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