How and Why Do Lightning Sferics have Unstructured Wavefronts

This article extends the mathematical model of the complete radiation patterns of the bremsstrahlung process, which involves bremsstrahlung asymmetry and Doppler shift. Firstly, the mathematical model is simplified, preserving the forward-backward peaking radiation properties and the involved asymmetries. This helped investigate and model the tendency of rotation in the wavefront of the emitted wave. Consequently, it has been found that the curl of the gradient of the radiation intensity is non-zero and the wavefront of the bremsstrahlung radiation follows a spiral wavefront in 2D and helical wavefront in 3D. The radius of the rotational wavefront was found to be decreasing as the wave propagates. Spiral geometry has different magnitudes of radius with respect to the direction of particle motion as the wavefront rotates. Hence, the different magnitudes of spiral wavefronts in 2D are the result of the involved bremsstrahlung and Doppler shift asymmetries. This is also supported diagrammatically by applying Huygens’s principle on a relativistic radiation pattern. Additionally, this is supported by the quantization of the bremsstrahlung asymmetry, R, through momentum transfer from the particle to the rotating wavefront photon, which is quantized via conservation of momentum. Outcomes describe why the lightning discharges display a partial temporal and spatial coherence, hence why lightning sferics are not known to produce structured wavefronts. Bremsstrahlung emissions start with a rotating and irregularly shrinking radius wavefront. Therefore, spatial coherency degrades as their helical structure breaks down due to the irregular shrinkage of radius. This leaves radiation from the bremsstrahlung process with partial temporal coherence.