We study how external magnetic fields from 0 to 40 T influence positive streamers in atmospheric pressure air, using 3D PIC-MCC (particle-in-cell, Monte Carlo collision) simulations. When a magnetic field B is applied perpendicular to the background electric field E , the streamers deflect towards the + B and − B directions which results in a branching into two main channels. With a stronger magnetic field the angle between the branches increases, and for the 40 T case the branches grow almost parallel to the magnetic field. Due to the E × B drift of electrons we also observe a streamer deviation in the opposite − E × B direction, where the minus sign appears because positive streamers propagate opposite to the electron drift velocity. The deviation due to this E × B effect is smaller than the deviation parallel to B . In both cases of B perpendicular and parallel to E , the streamer radius decreases with the magnetic field strength. We relate our observations to the effects of electric and magnetic fields on electron transport and reaction coefficients.

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Plasma Sources Science and Technology
Centrum Wiskunde & Informatica, Amsterdam (CWI), The Netherlands

Wang, Z., Sun, A., Dujko, S., Ebert, U., & Teunissen, J. (2024). 3D simulations of positive streamers in air in a strong external magnetic field. Plasma Sources Science and Technology, 33(2), 025007–025007. doi:10.1088/1361-6595/ad227f