Parts of the South Island were dazzled late last night by displays of pinks, greens and purples lighting up the sky — but why is that? 1News spoke to NIWA meteorologist Ben Noll to find out more.
To put it simply, the pretty colours in the sky, called aurora borealis if you’re in the Northern Hemisphere or aurora australis if you’re in the Southern Hemisphere, are a result of solar storms happening in space.
“There is a peak in the solar cycle,” Noll said. “The sun, every 11 years, goes through these periods of activity, followed by inactivity.”
This year, it has been forecast to peak, meaning the sun is having these solar storms more frequently. They will then start to reduce, meaning fewer chances to see the aurora australis or southern lights here in New Zealand.
“They are called sun spots. They’re bundles of energy occurring over the sun. Some are big, some are small,” Noll said. But how does that affect our skies?
“Those sunspots can have this effect where they snap, and they send out energy, electrons, pulses of energy outwards. Those are called solar flares, and when one of them blasts out towards Earth, when that energy reaches our magnetosphere, that energy can get translated to the pretty lights that we see.”
The magnetosphere is a region of space surrounding Earth which protects our planet from solar and cosmic particle radiation, as well as erosion of our atmospheres by solar wind, according to NASA.
The magnetosphere, in essence, strips the harmful radiation effects of the solar flares and turns it into a multicoloured display that can be seen through long-exposure cameras.
However, there is more at play than just the solar flares — timing plays a part as well.
“It can take 20-25 hours [for the solar flares] to get from the sun to the Earth, and if it just so happens to reach the Earth when it’s nighttime in your part of the world, it can lead to pretty amazing things,” Noll said.
If it’s daytime in your neck of the woods after a solar flare, you’re out of luck: “The light from the sun outshines the [solar flares], so we can’t see it during the day.”
Why are the aurorae different colours?
According to NASA, the colour of the aurora depends on which gases are being agitated by electrons and how much energy was being exchanged.
“Oxygen emits either a greenish-yellow light (the most familiar colour of the aurora) or a red light; nitrogen generally gives off a blue light.
“The oxygen and nitrogen molecules also emit ultraviolet light, which can only be detected by special cameras on satellites.”
Why do some places have aurorae quite often?
Noll told 1News that some places, such as Iceland and Greenland, have more aurorae shows than others due to their location in relation to the North and South Poles.
“The magnetic field, which is centred at the North and South pole, they are basically like lines, and that is where the aurorae can focus. That is why places like Iceland, Greenland, places near the North pole in the Northern Hemisphere [see the lights].”
That said, us in the Southern Hemisphere still have a chance to see the aurora australis, or southern lights, too.
“If you were in Antarctica, the frequency of seeing these things would be much higher. It’s a polar-focused event. but sometimes when the solar event is strong enough, that can affect parts of the Earth that are further away from the poles.”
“You need a more intense event to see it further away from the pole. At the [Southern] pole, it would be occurring more regularly and you would be able to see it with more frequency than we could in NZ. “
How to best capture images of the aurora
Technically speaking, aurorae is visible to the human eye, but it can be incredibly difficult to see. That’s why you’ll have a better chance of seeing the phenomenon through cameras.
“Cameras are more sensitive to low light than eyes, capturing details we can’t see in real-time,” Noll said.
“Cameras can enhance colours and use long exposures to accumulate light, making the aurora appear brighter and more colourful than we perceive it.”
“In essence, while the aurora is indeed visible to us, cameras can present it in a way our eyes can’t naturally match.”
To take the best images on your smartphone, you’ll need to go somewhere with minimal light pollution, as neighbouring lights can dilute the colours.
If you have an iPhone, enable night mode on your device. Turn off flash and increase your exposure — you want this to be at maximum capacity.
In your camera settings you’ll find a +/- icon. It’s a bit trial and error to find the best setting that works for you and your surroundings, but 0.7 is a good place to start.
Try to keep your phone as still as possible, or use a tripod for stability.
If you have an Android, it’s slightly different. Enable night mode, then turn your camera to either the ‘professional’ or ‘manual’ settings.
Toggle the ‘MF’ icon to focus the camera, and turn off the flash.
Adjust your ISO settings to 1600 or above, but ensure the white balance is set to around 3200K. Enable a long shutter speed in relation to how vivid the aurora is — 1-5 seconds for brighter displays and 20-30 seconds for dimmer displays.
Again, try and keep your phone as still as possible or use a tripod for stability.
Regardless of your device, you will have better results if you turn phone horizontally.
