Abstract
To model the ionization structure of the Orion nebula, we adopt a steep density stratification, increasing as a power-law ( n ~ x^-2) function of distance x from the ionization front. The line-ratio gradients observed along the slit are qualitatively reproduced by our density stratified models. Collisional deexcitation appears to be responsible for half of the gradient observed in the [N II] <~mbda 5755} / [N II] <~mbda 6583} temperature sensitive ratio.
