Look out for the rare electric blue luminous clouds in the northern sky

At that time of the year again, astronomical observers have the opportunity to see a rare, gleaming cloud in the evening sky.

The luminous clouds (NLC) or the middle polar clouds are breathtaking. These are not ordinary clouds. They are formed in the highest part of our atmosphere, 80 kilometers above sea level.

NLC is not that easy to understand. However, researchers believe they are caused by meteor dust in our upper atmosphere.

They are most prominent in the northern hemisphere during approximately June to July (although they may occur from May to August) and require three things to appear: an increase in water vapor, very cold temperatures, and water vapor can condense on them. Ice particles, such as dust from meteors (sometimes particles from rocket launches).

Similarly, the sun needs to be at least six degrees below the horizon to illuminate the clouds.

These clouds have been downgraded to extreme northern latitudes (or southern summers), but in the past decade, they seem to be moving south. In 2019, people saw them as far away as southern California.

Luminous clouds seen over the Upper Mission community in Kelowna, British Columbia on June 16. (Tara Kaman)

A kind Research in 2018 suggests that they may move south Due to climate change. The author claims that although NLCs may have been visible for centuries, they are too weak to be seen with the naked eye. But as the earth warms, there is more water vapor in the atmosphere, making them brighter. Now with climate change, there is more water vapor, especially in low latitude areas.

Another contributing factor may be the sun. The sun goes through an 11-year cycle, and solar activity (such as sunspots) increases and decreases. However, the past few cycles have been less active than in the past. When the sun is not so active, our middle layer will cool down. With the increase of water vapor and the cooling of the intermediate layer, it may create suitable conditions for the formation of NLC.

As for why they are blue, it is because of ozone. Sunlight reaching the clouds first passes through the ozone layer, which absorbs red light but allows blue light to pass through.

Luminous clouds seen from Kaleida, Manitoba at around 11pm on June 16 (Submitted by Sheila Wiwchar)

In the past week, many people from all over the country have seen luminous clouds, and many people in Alberta, Saskatchewan, and Manitoba reported that the sky was gleaming after sunset.

They were even seen to the southernmost point Oregon, Washington and Montana, and parts of Northern Europe.

But it’s not just the Earth that has experienced NLC.Just last month, NASA’s Curiosity rover Photograph the clouds on Mars.

If you want to see them with your own eyes, please start about 30 minutes after sunset or before sunrise and look north. The lower your latitude (below 50 degrees north latitude), the more likely they are to appear on the horizon, so it is best to reach a place with a clear view. Sometimes NLC is confused with cirrus clouds that may reflect sunlight. The main difference is that NLC is more slender and electric blue.

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