Observed one‐dimensional return stroke propagation speeds in the bottom 170 m of a rocket‐triggered lightning channel

Abstract

[1] The return-stroke propagation speeds of five strokes from a seven-stroke triggered lightning flash are measured, with a 2 ns sampling interval, using a vertical array of photodiodes. Various methods for determining the reference point to be tracked are explored, and the speed is seen to vary over nearly an order of magnitude depending upon which method is chosen. The speeds are generally in agreement with the values found in the literature. The return-stroke speed appears to increase with height and then decrease with height in four of the five strokes examined.

Electric and Magnetic Fields Predicted by Different Electromagnetic Models of the Lightning Return Stroke Versus Measured Fields

“…The modified type-2 model has nonuniformly distributed series resistance: R = 2 Ω/m for z = 0-0. for z = 4 to 7.5 km, and 5 Ω/m for z > 7.5 km. The specified resistance profiles with relatively high resistance within the bottom 0.5 km appear to be consistent with observed light profiles along both natural subsequent return-stroke channels [33] and rocket-triggered lightning channels [34], showing that the light intensity decays significantly with height near ground. The reason for assuming the relatively high channel resistance above 7.5 km is to diminish the current above 7.5 km.…”

A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

“…The wires unwind during rocket ascent to provide preferential high conductivity paths, where discharges are more likely to occur (e.g., Biagi et al, 2009). In some cases, aircraft flying within strong convective systems can trigger lightning (Mazur, 1989;Kito et al, 1995;Olsen et al, 2004;Jerauld et al, 2005). Statistically, each major aircraft is likely struck by lightning once a year and a well-known example is Apollo 12 being hit by lightning soon after takeoff (Rakov and Uman, 2007).…”

Analytical fields expressions due to lightning channel considering variation of return stroke velocities along the lightning channel

“…Several studies have been done to measure return stroke velocity along lightning channel whereas they showed the velocity along lightning channel is as a height dependent variable [1][2][3]. On the other hand, the measured return stroke velocities at first few meters heights along channel illustrate that the value of return stroke velocity is beyond c/3 to 2c/3 where c is speed of light in free space [1].…”

“…Keywords-electromagnetic fields; lightning channel; return stroke velocity INTRODUCTION Several studies have been done to measure return stroke front velocity along lightning channel while they showed a variable behavior for velocity at different heights [1][2][3]. On the other hand, the electromagnetic fields associated with lightning channel are depending on the return stroke velocity along channel when it is assumed as a constant value equal to average of velocities along channel in widely used calculation methods [4-6] and it can create an inherent error in the field calculations.…”