  This paper studies the turbulent kinetic energy ($k_\perp$) in 2D isothermal
electrostatic interchange-dominated ExB drift turbulence in the scrape-off
layer and its relation to particle transport. An evolution equation for the
former is analytically derived from the underlying turbulence equations.
Evaluating this equation shows that the dominant source for the turbulent
kinetic energy is due to interchange drive, while the parallel current loss to
the sheath constitutes the main sink. Perpendicular transport of the turbulent
kinetic energy seems to play a minor role in the balance equation. Reynolds
stress energy transfer also seems to be negligible, presumably because no
significant shear flow develops under the given assumptions of isothermal
sheath-limited conditions in the open field line region. The interchange source
of the turbulence is analytically related to the average turbulent ExB energy
flux, while a regression analysis of TOKAM2D data suggests a model that is
linear in the turbulent kinetic energy for the sheath loss. A similar
regression analysis yields a diffusive model for the average radial particle
flux, in which the anomalous diffusion coefficient scales with the square root
of the turbulent kinetic energy. Combining these three components, a closed set
of equations for the mean-field particle transport is obtained, in which the
source of the turbulence depends on mean flow gradients and $k_\perp$ through
the particle flux, while the turbulence is saturated by parallel losses to the
sheath. Implementation of this new model in a 1D mean-field code shows good
agreement with the original TOKAM2D data over a range of model parameters.
