The helix instability of a convection stabilized high current arc burning in a high pressure nitrogen gas flow is investigated theoretically and experimentally. Equations for the electric and magnetic fields and the current density are solved in helix coordinates for small displacements. The resulting electromagnetic force on a helix segment is calculated and compared to the gasdynamic stabilizing forces. A formula is derived for the growth rate as a function of helix pitch and the physical parameters current density and gas density. The comparison with experimental data yields good qualitative agreement for the onset and the growth rate of the helix instability.
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Ragaller et al. (1973) studied this question.