Calculation of Formative Time Lags in Dry Air in Crossed Electric and Magnetic Fields

A formula has been derived for the calculation of formative time lags in dry air with high applied overvoltages on the basis of temporal and spatial growth of ionization currents. The formula is then extended to a discharge in E×B fields by considering the influence of a crossed magnetic field on each of the parameters involved in the current build up process, according to the effective reduced electric field (EREF) concept. For the first time Somerville´s formula for the loss of electrons to the cathode in a magnetic field has been shown to be applicable in the calculation of formative time lags. At zero magnetic field and low magnetic field strengths, the calculated formative time lags in dry air agree very well with the measure values. Calculated formative time lags over a range of magnetic field strengths and over voltages are presented. In a strong magnetic field and high overvoltages, the time lag calculations show that the secondary ionization coefficient is entirely due to photoelectric action at the cathode.