We introduce a kinetic model for diffusion in spatially heterogeneous environments, such as those induced by variations in temperature or properties of the surrounding medium, and investigate the macroscopic diffusion equation arising from this dynamics.

In contrast to most existing kinetic models, where particle reorientation is governed by a turning frequency measured per unit time, we consider a framework in which the turning frequency is prescribed per unit traveled distance.

The aim of this work is to elucidate the analytical consequences of this spatially defined turning mechanism, to highlight its fundamental differences from the standard temporal formulation, and to characterize how the resulting macroscopic diffusion equation departs from diffusion limits derived from classical kinetic models.