Griffiths and Phelps Lightning Initiation Model, Revisited
Griffiths and Phelps Lightning Initiation Model, Revisited
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DOI：
10.1029/2019jd030399
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发表时间：
2019-07-27
影响因子：
4.4
通讯作者：
da Silva, Caitano L.
中科院分区：
文献类型：
--
作者：
Attanasio, Alex;Krehbiel, Paul R.;da Silva, Caitano L.
在这篇文章中，我们重建了格里菲斯和菲尔普斯的流光系统的开创性模型，以测试它是否能重现快速正击穿的关键观测特征。我们首先通过复制原始结果来确认我们的实施是准确的。该模型描述了一个正流光系统如何表现出作为位置或时间的函数的初始指数电荷增长，并迅速转变为二次稳态。电荷的增长伴随着起爆位置附近电场的显著增强，为闪电的发生创造了有利条件。由于流光的电导率相对较低(在该模型中实际上为零)，电场增强是由在传播的最初几米中沉积的电荷产生的，在该标度长度内，电荷增长从指数型转变为二次型。电荷的二次增长与锥形系统的展开相结合，使得运动前沿的表面电荷密度保持不变。流光系统前面产生的电场在传播过程中保持几乎恒定，这与快速击穿的观测结果一致，这表明传播速度几乎是恒定的，与放电极性无关。对模型的最小更改允许模拟窄的双极事件，非常好地再现其特征的双极电场变化波形。尽管格里菲斯和菲尔普斯的模型很简单，但它在快速正向击穿和闪电引发之间的关系上提供了有价值的物理见解。
In this paper we reconstruct Griffiths and Phelps' seminal model of streamer systems to test if it can reproduce the key observational features of fast positive breakdown. We first confirm that our implementation is accurate by reproducing the original results. The model describes how a system of positive streamers exhibits an initial exponential charge growth, as a function of position or time, which rapidly transitions into a quadratic steady state. The charge growth is accompanied by substantial electric field enhancement near the onset location, creating favorable conditions for lightning initiation. Due to the relatively low conductivity of streamers (effectively zero in this model), the electric field enhancement is created by the charge deposited in the first few meters of propagation, in the scale length where the charge growth transitions from exponential to quadratic. The quadratic growth of charge, combined with conical system expansion, makes the surface charge density of the moving front constant. The resulting electric field ahead of the streamer system remains nearly constant during its propagation, consistent with the observations of fast breakdown, which reveal a nearly constant propagation velocity, independently of discharge polarity. Minimal changes to the model allow for simulation of narrow bipolar events, reproducing very well their characteristic bipolar electric field change waveform. Despite its simplicity, the Griffiths and Phelps model provides valuable physical insights in the relationship between fast positive breakdown and lightning initiation.