Mechanism of structure of atmospheric lightning Lightning is a natural atmospheric phenomenon.From early childhood years we all are familiar with the concept of lightning.But recently,from a website named Z T RESEARCH,i came across the  fact that not  only lightning can occur from upwards but also from downwards,(Eg. From tall objects).When i further observed the pattern of lightning,it was somewhat familiar with the branches of the tree,including it’s subbranches.When i observed more i found out that initially when the lightning occurs,irrespective of from upwards or downwards,the structure initially takes the pattern of a subbranched tree(with both upwards and downwards branch) and finally settling into one single line.I am very new in this field and thus want to know how this structure is actually happening.
 A: A driven diffusive system with noisy relaxation, that which minimises net dissipation cost in the process of its stationary structure formation, is the one we observe in nature ubiquitously and with omnipotence.
Consider a tree, a lightning leader-streamer propagation [article], a river-basin structure or delta formation [article], blood vessels and neuronal structures of living systems, all entails the self-similar fractaled branching structures [article].
One can think of the dynamics of these kinds, being modelled in terms of Orstein-Uhlenbeck stochastic process, incorporates a hyperbolic parameter space, due to the standard theorem that: The Fisher-Rao Geometry over Gaussian distribution space is hyperbolic [article].
But the scale-invariance of such structure must entail a power-law somewhere which probably captures the limitting-geodesics of that hyperbolic Poincare disk model,as if the system in its non-equilibrium stationary state has some temporal long-range correlation, or simply, memory; thus inherits equivalent miniaturised structure at all scales,
but the physics community is devoid of an unified simple explanation of all such ubiquitous structure formation.
Regarding your doubt about upward-downward lightning, it's probably a misconception, i.e. the leaders carry the charges while streamers in a lightning dissipates it over the atmosphere, and as it reaches the ground, it dumps down the whole charge through the stable channel it creates along its trajectory, so the upward lightning you've seen in ZT_Research video, is the plasma glow, that first starts with high collision of the charge-dump near the surface, and reaches upwards.
