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Measurements of the growth rate of structure, $f\sigma_8$ in the low-redshiftUniverse allow stringent tests of the cosmological model. In this work, weprovide new constraints on $f\sigma_{8}$ at an effective redshift of $z=0.03$using the combined density and velocity fields measured by the 2MTF and 6dFGSvsurveys. We do this by applying a new estimator of the redshift-space densityand momentum (density-weighted velocity) power spectra, developed in the firstpaper of this series, to measured redshifts and peculiar velocities from thesedatasets. We combine this with models of the density and momentum power spectrain the presence of complex survey geometries and with an ensemble of simulatedgalaxy catalogues that match the survey selection functions and galaxy bias. Weuse these simulations to estimate the errors on our measurements and identifypossible systematics. In particular, we are able to identify and remove biasescaused by the non-Gaussianity of the power spectra by applying the Box-Coxtransformation to the power spectra prior to fitting. After thorough validationof our methods we recover a constraint of$f\sigma_8(z_{\mathrm{eff}}=0.03)=0.404^{+0.082}_{-0.081}$ from the combined2MTF and 6dFGSv data. This measurement is fully consistent with theexpectations of General Relativity and the $\Lambda$ Cold Dark Mattercosmological model. It is also comparable and complementary to constraintsusing different techniques on similar data, affirming the usefulness of ourmethod for extracting cosmology from velocity fields.

The Redshift Space Momentum Power Spectrum II: measuring the growth rate from the combined 2MTF and 6dFGSv surveys