The idea of “rainbow lightning” striking the ground is fantasy, as standard lightning is a brilliant white or blue-white electrical discharge. However, the atmosphere hosts spectacularly colorful electrical phenomena far above regular thunderstorms. These fleeting, high-altitude light shows are not traditional lightning strikes, but they are directly triggered by them. They represent the colorful electrical activity people often imagine when picturing vibrant, non-white storms.
The Scientific Reality Behind “Rainbow Lightning”
The atmospheric events often mistaken for “rainbow lightning” are collectively known as Transient Luminous Events (TLEs). These high-altitude electrical discharges take place in the upper atmosphere, far above the storm clouds. They are extremely brief and generally require specialized cameras to capture their full color and structure.
The most widely known TLE is the Red Sprite, which appears as a massive, short-lived reddish-orange flash high above a thunderstorm. Sprites can span tens of kilometers in width and height, reaching from 50 to 90 kilometers above the Earth’s surface. These towering discharges are a form of cold plasma, lacking the extreme heat characteristic of the lightning channel below.
Other TLEs include ELVES, which appear as rapidly expanding, reddish-tinged rings of light near 100 kilometers. Halos are diffuse, pancake-shaped glows that often precede a sprite, forming a broad reddish disc. These events are the upper atmosphere’s response to the powerful electromagnetic changes generated by a strong lightning strike occurring below the cloud tops.
Why Specific Colors Appear in High-Altitude Events
The distinct colors of TLEs, such as the prominent red of a sprite, result from the electrical discharge exciting specific molecules in the thin upper atmosphere. This process is similar to how a neon sign glows, where electricity energizes gas atoms to emit light. The reddish-orange hue of a sprite is primarily caused by the excitation of nitrogen molecules in the mesosphere.
Nitrogen is the most abundant gas in the atmosphere, and when electrically excited at the low pressures found between 50 and 90 kilometers, it emits strongly in the red spectrum. Lower down, the sprite’s tendrils sometimes exhibit a bluer or purplish tint. This color change is still due to nitrogen, but it is excited by electrons moving at higher speeds in the slightly denser air at lower altitudes.
The varying colors across a single event, from reddish-orange at the top to bluish at the bottom, reflect the changing density and electrical properties of the atmosphere at different altitudes. This molecular excitation process differs scientifically from the intense, superheated white light produced by a standard lightning bolt. The combination of high-altitude gases and low pressure dictates the colorful visual outcome.
How Transient Luminous Events Differ from Standard Lightning
Transient Luminous Events occur in a completely different part of the atmosphere than the familiar strikes we see during a storm. Standard cloud-to-ground lightning forms within the troposphere, the lowest layer of the atmosphere, typically below 15 kilometers. Conversely, TLEs originate in the mesosphere and ionosphere, layers ranging from 40 to over 100 kilometers above the ground.
The mechanism creating these high-altitude events is fundamentally different from a regular lightning bolt. Standard lightning is a massive flow of electrical current that creates an intensely hot channel of plasma. TLEs, particularly sprites, are triggered by the powerful electromagnetic pulse and the sudden change in the electrical field following a strong, positive cloud-to-ground strike.
TLEs are extremely short-lived, often lasting less than a few tens of milliseconds. Standard lightning, while appearing instantaneous, is much more visible to the naked eye and involves a much higher current flow. TLEs are essentially a high-voltage, low-current cold plasma response to the charge imbalance created by the powerful storm below.