Effects of spatial non-uniformity of streamer discharges on spectroscopic diagnostics of peak electric fields in transient luminous events

The electric fields associated with streamer discharges in transient luminous events (TLEs) have been recently measured by considering the ratios of spatially integrated radiation intensities of band systems with different energy excitation thresholds. Following recent work by Naidis (2009) we demonstrate that due to strong spatial variations of the electron density and electric field in streamer heads such measurements may lead to a significant underestimation of the peak values of electric fields. The modeling analysis of streamers as a function of altitude, applied reduced electric field, and streamer polarity indicate that the ratios based electric fields derived from spectrophotometric data need to be multiplied by a corrective factor >1.4 for positive streamers and >1.5 for negative streamers, to obtain the true peak values of electric fields.