Aims. Solar Orbiter (SolO) was launched on February 9, 2020, allowing us to study the nature of turbulence in the inner heliopshere. We investigate the evolution of anisotropic turbulence in the fast and slow solar wind in the inner heliosphere using the nearly incompressible magnetohydrodynamic (NI MHD) turbulence model and SolO measurements. Methods. We calculated the two dimensional (2D) and the slab variances of the energy in forward and backward propagating modes, the fluctuating magnetic energy, the fluctuating kinetic energy, the normalized residual energy, and the normalized crosshelicity as a function of the angle between the mean solar wind speedmore »
This content will become publicly available on January 1, 2023
Inertialrange Magneticfluctuation Anisotropy Observed from Parker Solar Probe’s First Seven Orbits
Solar wind turbulence is anisotropic with respect to the mean magnetic field. Anisotropy leads to ambiguity when interpreting in situ turbulence observations in the solar wind because an apparent change in the measurements could be due to either the change of intrinsic turbulence properties or to a simple change of the spacecraft sampling
direction. We demonstrate the ambiguity using the spectral index and magnetic compressibility in the inertial range observed by the Parker Solar Probe during its first seven orbits ranging from 0.1 to 0.6 au. To unravel the effects of the sampling direction, we assess whether the wavevector anisotropy is consistent with a twodimensional (2D)
plus slab turbulence transport model and determine the fraction of power in the 2D versus slab component. Our results confirm that the 2D plus slab model is consistent with the data and the power ratio between 2D and slab components depends on radial distance, with the relative power in 2D fluctuations becoming smaller closer to the Sun.
 Award ID(s):
 1655280
 Publication Date:
 NSFPAR ID:
 10312699
 Journal Name:
 The Astrophysical journal
 Volume:
 924
 Issue:
 L5
 ISSN:
 15384365
 Sponsoring Org:
 National Science Foundation
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