Magnetic field effects on the propagation of positive streamers

We investigate how strong magnetic fields affect the propagation of positive streamer discharges. Because such discharges grow opposite to the electron drift direction, they require a source of electrons ahead of them. Here we focus on air, in which photoionization supplies such free electrons isotropically around the streamer head. Using a 3D particle model, we investigate how strong transverse magnetic fields alter the trajectory, ionization rate and energy of these source electrons, leading to streamer branching in the plane spanned by E and B.