Fox Fires 2: Expectations
To have a great aurora experience, it is good to have realistic expectations. Not living in a place where auroras are visible often leads to wrong assumptions. To give you a better picture of what to expect, I will go through some common questions and answer them to my knowledge. As you read through, you will understand that there are many uncertainties in predicting auroras.
This question is on purpose the number 1 in this list, because it is – in my humble opinion – one of the most important. The short answer is: Only in few cases.
For the human eye, the colors of the Northern lights are much weaker. The reason for this is the difference between the 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 onto its sensor and creates one image from all those single moments. Therefore the colors are mostly stronger in the image opposed to how we see them. Imagine a white piece of paper and a green crayon. If you stroke once gentle, you can barely see the color. If you keep stroking for 5 seconds, the color visible will be stronger.
Trying to photograph auroras exactly as the human eye sees it, is nearly impossible. It would result in a black landscape because there just isn’t enough light. Our eyes see pale aurora colors but at the same time we see the landscape. Eye or camera? There is more than one truth.
For you to have a better idea what you might see, I edited some photos the way the camera sees it compared to how I saw it.
Due to a technical challenge please click here to see the comparisons
1. Common, the green color is visible but red and purple nearly without color:
2. Seldom, when the red becomes visible it is there for quite a while moving only slowly.:
3. Very seldom, during a strong geomagnetic storm, nearly all colors were visible:
No, every night is different. Green is the most common color, followed by purple, red and blue. Fast-moving green arcs can have white/purple color at the lower end, which is very bright in visible to the eye.
When the charged solar particles collide with atoms in our atmosphere, these atoms get excited. During the return to normal state the atoms release colors. 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 and probably low altitude red-pink.
Shapes are mostly determined by the strength and speed of the solar wind. Depending where you are to view auroras, some shapes will be more common than others. Let’s go through some of the common shapes, starting with the relatively calm ones, arcs, high needles and curtains.
Weak solar wind might create ‘only’ a very pale, green ‘fog’ or low arc on the horizon which -to the eye – barely moves at all. With speed and strength picking up, that arc comes to life and moves faster. It can turn into a curtain with needles rising high up in the sky. 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 moving it back and forth creating waves. During stronger nights there are multiple arcs spread over the sky.
Let’s go to the crazy stuff like spirals, coronas and flickering
Spirals travel from the low horizon upwards and dance in curves. This is often happening with strong solar wind. If this happens relatively high, you will start to see countless needles rushing through. Once right above, a corona will most likely open up. Countless rays spread out in multiple colors. This usually lasts only for a short time as the aurora moves on. Towards the end of the night, there is often a kind of flickering, where parts of the sky above are randomly lit up by weak auroras and switched off within split-seconds.
Usually a mix of these shapes will appear in the sky, including shapes that were not described here. As with nearly everything aurora-related, every night can be different.
Not usually, this depends on the strength and density of the solar wind flowing into our atmosphere. A long-lasting strong CME or big coronal hole can produce a show that lasts throughout the night and longer. During some nights the show may last only for a short time.
No, it all depends on what is happening on the sun and solar wind. 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. During solar minimum might be even a very long period.
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.
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 (the distance is 150 million kilometres), impact is usually around 24-72 hours afterwards. However, sometimes there may be no impact recorded at all.
The estimate for time of impact is not always correct, sometimes it is earlier, sometimes later. Another uncertainty.
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 in real-time, magnetograms showing 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 helpful links including these and more.