  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
either to 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 two-dimensional (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.
