  We consider 2D joint distributions of normalised residual energy
$\sigma_r(s,t)$ and cross helicity $\sigma_c(s,t)$ during one day of Parker
Solar Probe's (PSP's) first encounter as a function of wavelet scale $s$. The
broad features of the distributions are similar to previous observations made
by HELIOS in slow solar wind, namely well correlated and fairly Alfv\'enic,
except for a population with negative cross helicity which is seen at shorter
wavelet scales. We show that this population is due to the presence of magnetic
switchbacks, brief periods where the magnetic field polarity reverses. Such
switchbacks have been observed before, both in HELIOS data and in Ulysses data
in the polar solar wind. Their abundance and short timescales as seen by PSP in
its first encounter is a new observation, and their precise origin is still
unknown. By analysing these MHD invariants as a function of wavelet scale we
show that MHD waves do indeed follow the local mean magnetic field through
switchbacks, with net Elsasser flux propagating inward during the field
reversal, and that they therefore must be local kinks in the magnetic field and
not due to small regions of opposite polarity on the surface of the Sun. Such
observations are important to keep in mind as computing cross helicity without
taking into account the effect of switchbacks may result in spurious
underestimation of $\sigma_c$ as PSP gets closer to the Sun in later orbits.
