What Causes and How are Lightning Sprites Formed?

I f as a child you used to be extremely passionate about astrology and natural phenomena, you’ve probably heard about and even seen lightning sprites (or photos of them) on occasion. But if you’re completely unaware of what that is, don’t worry, you’ve come to the right article.

Lightning sprites, or red sprites as they are often referred to, are usually seen in clusters of at least two, and they have been compared to jellyfish, tree roots, carrots, or even the nervous system of the human body, appearance-wise. When it comes to their color, they are often an intense red orange, or even a golden gate orange on the upper ‘bursting flames’ portion, and towards the ends of the tendrils they can have a hint of blue. Without further ado, let’s learn more about these interesting phenomena!

Lightning Sprites Forming

Initial sightings

The name ‘sprite’ means ‘air spirit’ and they are called so because of how elusive they are. So much so, that the first visual records happened in the 19th century around the year 1886 and they came from pilots who reported seeing strange lights. Fast-forward, the sprites were predicted by C. T. R. Wilson in the year 1924, but it took another 65 years until the first video evidence shot by John R. Winckler. In July 1989, the experimental physicist was testing a low-light television camera and managed to capture the first documented proof of lightning sprites. Later on, in 1994, on the 4th of July, the first photographic proof came to life thanks to scientists of the University of Michigan.

What are they, really?

Put simply, these sprites are a mechanism with the help of which electrical charges are being dispersed on a vertical route. They are often the suitors of regular lightning bolts, but only those that are especially powerful and charged positively. Regular lightning can happen without a sprite apparition, but sprites cannot happen without regular lightning.

In scientific terms, the material of these discharges is cold plasma because, as opposed to the usual bolt, it lacks the high channel temperatures and it also occurs higher than the former. With the help of a professional camera (10.000 fps), it was concluded that the clusters are composed of balls of ionization, with sizes between 33 and 328 feet, that are sent flying downwards from a 50-mile altitude, with speeds up to 10% of that of light. Those are immediately succeeded by another group of ionization balls, only those move upwards.

How do they form?

Going into even greater detail than what they look like and what they are, now we’ll analyze how they form and mention what types of sprites exist. Knowing how this happens is crucial because of the interference and disruptions they can cause to HF communication and radio waves. Those signals operate in the ionosphere where they can be properly propagated thanks to the reflections from ionized layers.

When sprites happen, they appear near extremely charged particles or at the irregularities in plasma, and they change the lower layer of the ionosphere (from 30 to 600 miles up) by affecting its electrical properties. They form in the mesosphere, the layer which is from 31 to 53 miles up, above the stratosphere and the troposphere. The troposphere (from 5 to 9 miles up) is the layer in which Cumulonimbus (thunder clouds) gather and create thunderstorms, the natural phenomena that is present with every sprite formation. Although some think that they only happen on rare occasions, this is not true. It only seems that way because of the speed with which they go from appearing to disappearing, which is less than a 10th of a second. This is the reason why they are called ‘elusive’ time and time again.

Lightning Sprites Over Clouds

The 3 types that were classified by Rodger in the year 1999 based on their appearance are:

• The Columniform Sprite – resembles a column shape and has multiple big discharges
• The Jellyfish Sprite – probably the largest (even 31 x 31 miles), it seems like the shape of a jellyfish, with a wider head and multiple soft ‘legs’
• The Carrot Sprite – because of its long tendrils, it has an aspect that resembles a carrot

On occasion, approximately 43 miles higher, a Halo precedes these discharges, showing itself maybe one millisecond before the actual sprite. The color matches, with the same red hue, and it looks just like an angel’s halo. The way it forms is similar, with the difference that its process is too weak, thus rendering it unable to get into the same shape.

How can you see a red sprite?

Red sprites aren’t as rare as you might think. They happen quite often and are fairly easy to see due to this. The reason why not a lot of many people have seen them is that most don’t even know about their existence. If you want to see the spectacular weather phenomenon, here is what you have to do:

• Red sprites occur during big thunderstorms with intense ground-level lightning. June is the best month to witness this sort of weather, but you should generally have big storms in other months during spring and summer.
• Light pollution needs to be as low as possible for you to see the sprites clearly. Obviously, the storm has to happen at night too when the sky is as clear and as dark as possible.
• To have the best view possible, the storm should be approximately 100-200 miles away from you. This way, you can see above the clouds.
• If the weather report announces big thunderstorms at 100-200 miles away from your location, check at what time they are supposed to happen, and get out sooner than that. This is because you need about 20 minutes of looking at the dark sky so that your sight adapts to the conditions. As the thunderstorm begins, concentrate on the area above the clouds, ignoring the normal lightning flashes until you finally see a red sprite.

The answer behind why they appear

We know the who, we know the how, now let’s look at the why. The reasons behind these red lights has been discussed oftentimes in past centuries, but some findings still aren’t conclusive to this day. Scientists say that the appearance of these sprites is prompted by very strong, positively charged, thundercloud-originated lightning bolts that strike the ground heavily. These perturbations, as they are called, need to be small-sized but very ample. If one of the two differs, two outcomes can occur:

1. If the size of the lightning happens to be too large, it won’t initiate the sprite elements and nothing will happen. This is because the bolt spreads too much, causing the intensity to mellow down and disperse differently.
2. If the lightning doesn’t have an amplitude that is high enough, the appearance time of the sprite is stalled for quite a while. This second one has been proven by using cameras with a higher speed, the resulting images capturing the presence of a halo for longer than usual, followed by the apparition of a sprite.

Other possible theories that haven’t been 100% proven, but are thought to cause sprites:

• Sprites will appear in an area where one has previously formed. It is thought that an area in which these irregularities have happened before still meets the needed criterion to cause another such event.
• The movement of meteors in the ionosphere could beckon irregularities that might trigger a sprite. As they move in the upper portion before combusting in the lower one, meteors can create a good environment for these discharges.

How to photograph them

As we’re sure we might’ve sparked something in those of you who are photography enthusiasts, here are a few tips on how to capture a sprite on camera.

• Use a long exposure camera (with a low shutter speed) or a recording camera that is sensitive to the color red. These types of equipment are used because of how fast they disappear.
• Make sure you are between 93 and 311 miles away from a busy thunderstorm, but that you also have a good, unobstructed view of it.
• Try to photograph them on a day when the sky is as unlit as possible. This is because any bit of extra light in the sky can mess with the exposure and cause a washed-out photo, ‘erasing’ the sprite from the shot.
• Good luck!

In conclusion

Maybe you’ve heard of them before, maybe you haven’t, but for us one thing is certain. We hope that you’ve found any bit of this information interesting or structured in a way that helped you understand this interesting phenomenon better. And we really hope that the day comes when you witness it in real life to see the beauty of nature at work in one of its most fascinating ways.