  We study Lagrangian statistics of the magnitudes of velocity and pressure
gradients in isotropic turbulence by quantifying their correlation functions
and their characteristic time scales. It has been found that the Lagrangian
time-correlations of the velocity and pressure gradient tensor and vector
elements scale with the locally-defined Kolmogorov time scale, defined from the
box-averaged dissipation-rate and viscosity. In this work, we study the
Lagrangian time-correlations of the absolute values of velocity and pressure
gradients. We explore the appropriate temporal scales with the aim to achieve
collapse of the correlation functions. The data used in this study are sampled
from the web-services accessible public turbulence
database(http://turbulence.pha.jhu.edu). The database archives a
pseudo-spectral direct numerical simulation of forced isotropic turbulence with
Taylor-scale Reynolds number 433, and supports spatial differentiation and
spatial/temporal interpolation inside the database. The analysis shows that the
temporal evolution of the auto-correlations of the absolute values are
determined not by the local Kolmogorov time-scale but by the local
eddy-turnover time scale. However, considerable scatter remains and appears to
be reduced only after a further (intermittency) correction factor of the form
of $(r/L)^\chi$ is introduced where $L$ is the turbulence integral scale. The
exponent $\chi$ varies for different variables. The collapse of the correlation
functions for absolute values is, however, less satisfactory than the collapse
observed for the more rapidly decaying strain-rate tensor element correlation
functions.
