Thursday, September 1, 2022

What determines the color of lightning?

Lets start with What is lightning?

Lightning is a violent and sudden electrostatic discharge where two electrically charged regions in the atmosphere temporarily equalize themselves, usually during a thunderstorm. When a bolt is released, the surrounding air is rapidly heated, causing it to expand violently at a rate faster than the speed of sound, similar to a sonic boom. At about 10 m out from the channel, it becomes an ordinary sound wave called thunder.

Thunder is effectively exploding air, and when heard close to the lightning, it consists of one large bang. At about 1 km away, it is heard as a rumble with several loud claps. Distant thunder has a characteristic low-pitched rumbling sound. However, beyond 16 km, thunder is seldom heard.


How does it occur? 

Lightning is an electrical current which can either travel across the sky or towards the ground. The thunderstorm which lightning develops within becomes electrically charged. The lighter, more positively charged particles develop at the top of the thunderstorm and the heavier, more negatively charged particles sink to the bottom of the thunderstorm (near the base). When these the charges grow large enough, then a giant spark occurs which is what we know as lightning. 


The majority of lightning happens within the cloud due to the attraction between positive and negative charges. If the surface of the Earth becomes intensely positively charged, then the attraction between negative charges in the base of the cloud and positive charges on the surface of the Earth have the ability to cause cloud to ground lightning. If these positive charges flow through things such as buildings, trees, lightning conductors or even people… then there is a chance that the lightning will strike these objects instead of the ground.




Types of lightning? 

(CG) Cloud to Ground

(CC) Cloud to Cloud

(CA) Clear-Air Lightning Strike

Blue Jets

Red Sprites

Elves





Now finally we get to your question.... What color is lightning?


Dust, moisture, temperature and air composition all impact the color of the flash. The bolts come in a variety of colors – white (most common); orange; blue, lilac, yellow, violet, sometimes green, red, and cyan. It can take any color in the full visible spectrum. The temperature of it also affects what color we see. The hotter it is, the closer to the end of the spectrum the color is**.** Its temperature can get as high as 50,000 degrees Fahrenheit which is hotter than the heat on the sun’s surface. Also, the distance between the bolt and the observer can impact what they see. As the rays of it travel through the atmosphere to the observer, it gets scattered by tiny dust particles in the air which make it take on different colors. The air’s composition affects how a bolt flashes for example instance, oxygen and nitrogen molecules in the air are so tiny that they tend to scatter light rays with short wavelengths.


The colors can provide insight into what to expect during a thunderstorm:


Blue lightning is an indication of a high-precipitation with hail. It is likely acquired the blue hue from light scattering property of tiny atmospheric particles which are also responsible for reflecting the radiations from the sun resulting in the blue sky.


Purple or lilac-tinted lightning bolt is often caused by high atmospheric humidity; which means the thunderstorm is accompanied by high-precipitation.


Yellow lightning is uncommon; however, they tend to be cooler than the blue, lilac and white. They’re caused to due to a high concentration of dust in the air. And is an indication of a dry thunderstorm with low-precipitation.


White lightning is the hottest, and literally, all bolts radiate white color. They’re an indication of a low concentration of moisture and dust in the air. These tend to ignite forest fires too.


Red lightning within a cloud indicates the presence of rain.


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