  In-situ observations of magnetic field fluctuations in the solar wind show a
broad continuum in the power spectral density (PSD) with a power-law range of
scaling often identified as an inertial range of magnetohydrodynamic
turbulence. However, both turbulence and discontinuities are present in the
solar wind on these inertial range of scales. We identify and remove these
discontinuities using a method which for the first time does not impose a
characteristic scale on the resultant time-series. The PSD of vector field
fluctuations obtained from at-a point observations is a tensor that can in
principle be anisotropic with scaling exponents that depend on background field
and flow direction. This provides a key test of theories of turbulence. We find
that the removal of discontinuities from the observed time-series can
significantly alter the PSD trace anisotropy. It becomes quasi-isotropic, in
that the observed exponent does not vary with the background field angle once
the discontinuities are removed. This is consistent with the predictions of the
Iroshnikov-Kraichnan model of turbulence. As a consistency check we construct a
surrogate time-series from the observations that is composed solely of
discontinuities. The surrogate provides an estimate of the PSD due solely to
discontinuities and this provides the effective noise-floor produced by
discontinuities for all scales greater than a few ion-cyclotron scales.
