Is lightening DC or AC?

Lightning is most accurately described as a powerful pulse of Direct Current (DC), but it is not a steady DC like from a battery. The current flows primarily in one direction, but the intensity and even the direction can vary within a single strike due to multiple return strokes, making it a chaotic and pulsed form of DC. 

Why it's considered Direct Current (DC):

One-way flow:

The fundamental characteristic of a DC current is its flow in a single direction. In a typical lightning strike, the electrical current moves from the cloud to the ground or vice versa in a dominant direction. 

Capacitive discharge:

Lightning is a discharge of static electricity built up in a thundercloud, similar to a massive capacitor discharging. This type of discharge results in a single, albeit complex, event with a prevailing flow direction, which is a DC characteristic. 

Why it's not a steady or "pure" DC:

Pulsed nature:

A lightning strike isn't a constant current. It involves a series of pulses and return strokes that can vary in intensity over milliseconds, making it a dynamic, pulsed DC. 

Variable direction:

While the overall flow is in one direction, the specific direction of the current can change depending on whether the cloud is positively or negatively charged relative to the ground. 

Impulse current:

Some scientists prefer the term "impulse current" to describe lightning, as it's a more accurate representation of a very high-power pulse of electricity that lasts only a fraction of a second. 

In summary: While not pure or steady DC, the predominant, single-direction flow of charge in a lightning strike makes it fundamentally a form of direct current, not alternating current (AC).