Lunar coronae

The past weeks have been extremely busy with tours, preparations, studies and last but not least family time. Oh, and some other projects but I will talk about those another time.

A few days ago I returned from a tour in Lapland. Most nights were cloudy but luckily we also saw auroras. But that wasn’t all, the moon gave us a special show. The nights were around -15..-25C and fog pads were in the air. Due to the cold temperature it consisted of ice crystals. Sometimes the high clouds were just perfect to create multiple moon coronae (at least I think thats the correct term). The colors and shape were very distinct, something totally new for me. For a while I forgot about auroras :D. So, here it is. Winter wonderland under a wonderous moon.

Lunar coronae in Lapland, Finland.

An April aurora adventure

A few nights back on April 11/12 2014, wonderful auroras appeared in the skies above Oulunsalo, Finland. I’ve been out with my cameras for six hours, almost half of that time waiting for clouds to go away. At times I couldn’t see any stars but more often than not…

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… auroras were visible through through the clouds. Here you can see an arc rising and on the right are some needles. Wind brought more clouds and I was considering to leave.

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Fortunately I didn’t give up and later the clear skies revealed a wonderful surprise for me. There was an aurora arc and it went all the way up over my head and down on the other side!

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Around 1am the arc got stronger and wider and suddenly exploded over the frozen lake revealing countless needles…

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… which turned into a corona right above my head. The feeling when those rays spread out in all directions cannot be described. Look at this!

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An hour or so later, another strong but not so colorful corona was visible…

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… and I stayed until dawn made it difficult to see auroras. On the right you can see the beginning of the sunrise. An amazing night came to an end and it took me a long time to fall asleep 🙂

Fox ­fires – an Aurora Borealis guide II: Expectations

Part I: Introduction and Terms

To have a great aurora experience, it is good to have realistic expectations. Not living in a place where auroras are visible may lead to wrong assumptions. To give you a better picture of what to expect, I will go through some common questions and answer them. As you read through, you will understand that there are many uncertainties in predicting auroras.

Are the colors as strong as in the pictures I’ve seen?
Not often, the colors of auroras are usually much weaker to the human eye. There is one big difference between a camera and our eyes. If we look at the sky for five seconds, the human eye sees every moment once. We may remember them in our brain, but our eye can see only one moment a time and erases the one before. If the camera ‘looks’ for five seconds at the sky, it adds all moments together and creates one image from all those single moments. Therefore the colors are mostly stronger in the image opposed to how we see them.
Trying to photograph auroras in its natural, pale colors and strength would most of the time result in a black landscape because there just isn’t enough light.

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How the camera sees things (developed RAW)

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Here I tried to reconstruct how it really looked like

Are there always multiple colors of auroras in the sky?
No, every night is different. Green is the most common, followed by purple, red and blue. Strong green aurora arcs have often a bit of white/purple at the lower end.

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Nothing but green

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Very colorful aurora during geomagnetical storm

Why are there different colors?
Colors appear when gas in our atmosphere is excited by incoming solar wind. Oxygen then can produce the common green color and also the red in high altitudes. The color depends how excited the gas is. Nitrogen is responsible for blue. At times these colors mix and we can see purple, white, etc.

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Common green with red high above

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Green with white and purple at the lower edge

In what shapes do auroras appear?
Shapes are determined by the strength and speed of the solar wind. Depending where you are to view auroras, some shapes may be more common than others.
Let’s go through some of the common shapes and start with the relatively calm ones, arcs, needles and curtains:
Slow, weak wind might create ‘only’ a very pale, green arc on the horizon which barely moves at all, just like a rainbow. With speed and strength picking up, an arc may be higher up and even travel all the way over the sky. There are also times when you can see multiple arcs, one almost above you and others towards the horizons).
The arc can turn into a curtain with needles rising high up in the sky and travel fast through the arc. I like to call this a curtain because it reminds me of a stage curtain in a theater. Usually I imagine someone is at one end of that curtain making waves.

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An arc stretching over the horizon with some needles.

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A curtain made of countless needles

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A green curtain over the frozen Baltic Sea

Sometimes there is no curtain, arc or needles but a fog-like glow filling half the sky.
Let’s go to the crazy stuff now, spirals, coronas and flickering
Spirals travel from the low horizon upwards and dance in curves. This is often happening with strong solar wind and over in just a few minutes. If the auroras are very strong and you are lucky, you can see a corona opening up right above in the sky. Countless rays spread out in multiple colors. This usually lasts less than a minute. After a corona there is often a kind of flickering, where parts of the sky above are randomly lit up and switched off within split-seconds.

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Spiral shaped aurora with twilight

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Corona explosion in green and purple

Can I see auroras right after sunset?
No, auroras will be visible only once the sun is about 10 degrees below the horizon. Before that, the daylight is still too strong. In autumn there can be twilight at the horizon and auroras in the sky.

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Auroras with twilight on the horizon

Are the lights dancing in the sky all night long?
Not usually, this depends on the strength and density of the particles flowing into our atmosphere. However, a long-lasting strong CME or big coronal hole can produce a show that lasts throughout the night and longer.

Can I see Northern lights every night?
No, it all depends on what is happening on the sun and solar wind leaving. If the activity on the sun is high, there can be auroras for many nights in a row. When the sun is quiet, there can be a number of nights without any auroras.

Can auroras be seen through clouds?
Yes and no, it depends on the thickness of clouds. Through a thin layer of clouds, strong auroras can be seen easily. If the sky is filled with thick clouds there is usually no chance to see any auroras.

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Auroras visible through openings in the clouds

A CME erupted, when can I expect to see auroras?
That depends on a few things. First of all, for auroras to show up, that CME must travel towards Earth or at least near it. In case it does flow towards Earth, impact is usually around 24-72 hours afterwards. However, sometimes there may be no impact recorded at all.
The estimate for time of impact not always correct, sometimes it is earlier, sometimes later. The main reason for it is speed as we can’t know for sure how much the solar wind slows down while travelling.

I read online that there should be Northern lights tonight, is that a guarantee?
By now you have probably learned that there are no guarantees. The best way to know is to go outside and look up. Of course there are tools online which can help you. These include webcams showing the night sky, magnetograms showing how the situation of Earth’s magnetic field and pages showing the expected kp-index or auroral oval. The last part of this guide consists of a list of links.

We are at the end of the second part, expectations.
Continue reading:
Part III: Preparation is everything
Part IV: Photographing auroras
Part V: Links

A night out

When I saw auroras for the first time I did not understand anything about it, for me it was mysterious and I couldn’t stop looking. It was pure magic. Meanwhile years have passed and I try to see as many aurora shows as possible. I hardly can imagine anything better than being outside at night, equipped only with my camera gear and some tea. Waiting all alone in a forest, an open field, on a frozen lake or on the top of a hill is very exciting, believe it or not! Once the sky turns green all those hours are worth it.

On March 15th 2013 there was a huge eruption on the sun’s surface. Two days later the solar storm hit Earth. It was a special night for me and now I’ll take you along with me.

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Dark enough – the first photo of that night

Our journey starts just past noon on March 17th. I went online to check www.spaceweather.com for any updates of when the storm would hit. To my horror it already started in the morning! One of my worst fears might become reality: The storm would last only during daylight here in Finland.

At 5 pm the storm was still strong and my fear changed into hope. I figured the best chance to see auroras would be right after dusk. Sunset was at 6.24pm which meant that I needed to be at my spot around 8pm.

I charged batteries, filled the thermos with tea and got dressed. At 6.50pm I was ready to go. On the way a friend called, so I stopped the car to have a chat. It was not completely dark yet but I opened the window, put my head outside and looked straight up. The first green was already visible! As quickly (and politely) as possible I ended the call and drove the last kilometers like a maniac.

Out of the car the skies were clear, no auroras. I needed to walk about half an hour to reach my spot. After 50 meters ‘all hell broke loose’, I can’t describe it any differently. Lots and lots of auroras appeared, bright arcs, needles in green and purple, dancing like crazy in the bluish sky! At first I couldn’t move, it was so amazing. Then I shouted out loud, singing and jumping around like a boy in a candy store.

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Overwhelming – corona opening up

It took a good while before I remembered that I actually wanted to take pictures as well! I quickly set up the tripod and camera and started taking pictures into one direction. Then I looked behind me and saw a green arc travelling right through the moon, it was so strong. Gotta take pictures of that!

At one point I realized my car was in the frame. Seeing all these great auroras above my car, I swore to myself. It could be over any minute. Anyway I took my backpack, camera & tripod and ran about hundred meters through the snow. I looked straight up and saw the most beautiful corona opening up. Got to move the camera! After that the sky calmed down while I tried to understand what I just saw.

On the path were high trees towards South, so I needed to get to my spot from where I had a good few into all direction. I walked for a while but had to stop again. The next color wave came!

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Path of light – where I walked. On the left the moon behind the trees.

Eventually I got to my spot, after almost three hours. I stayed for a long time, seeing amazing things in the sky and even drank some tea. What a wild night! When I got home and tried to sleep, all I saw were auroras dancing in my mind. No chance to sleep, yet…

That was it; a trip with me on this special night. If you want to comment or had similar experiences, I’d be happy to read from you!

Thomas

PS: Photos in bigger resolution on 500px. You can follow me also on facebook or google+,