Modeling of the air plasma near the tip of the positive leader

With the aim of elucidating the role of thermal effects in air in the leader propagation, the properties of the ionized air (charged species densities, electric field, and air temperature) in a limited region near the tip of the positive leader were calculated using a two-dimensional axisymmetric numerical model. Charged-particle densities and the electric field were treated consistently. Compared with the geometrical field, the actual electric field appears to be much more uniform and is strongly reduced at the tip due to the plasma shielding. As a consequence of the field damping, thermal effects are determined to play a negligible role outside the leader boundary.