Flying Straight Into the Southern Geomagnetic Storm

For the past 12 months, global travel plans have come to a grinding halt as the result of the Covid-19 pandemic and whilst our region of the world has managed a little fairer, leaving our home countries has not been applicable unless it was deemed absolutely necessary.  

However, a handful of lucky New Zealanders were able to jump onto several special flights earlier this month, headed not to any destination in particular – but rather to circle the southern skies during a dazzling display of the Aurora Australis – the southern lights that occur near the Earth’s south pole.

Flights were hosted through Air New Zealand, working in partnership with Viva Expeditions and included onboard astronomers providing flight direction as to the best opportunity to follow the bright lights in the atmosphere, as well as running astronomical commentary for the guests.

Ticket prices for the flights were starting at roughly \$1,200 for the opportunity to experience an event that was likely a ‘once-in-a-lifetime’ for most people, which meant they were snapped up fairly quickly, with waitlists confirmed for all flights.

Astronomer and Director of Otago Museum in Dunedin, Dr. Ian Griffin, was onboard providing information to the passengers about the interplay of processes that were occurring outside of the aircraft.

“The flights last week were my eighth and ninth times flying into the southern auroral oval. Every flight has been different and these trips provided yet more excitement.” 

“The first flight on 20th and 21st March was simply amazing. We basically flew into a minor geomagnetic storm. The aurora was so bright it could be seen in twilight from about 20 minutes after we left Christchurch. We spent nearly seven hours of the ten-hour flight flying through an amazing pulsing display and I got some incredible pictures,” he said. 

“The coolest thing about this flight was we had special permission to turn off all external lights on the aircraft to improve viewing conditions for the passengers. We believe this was a world first! The astronomers on board christened this “stealth mode” although that probably doesn’t go down well in flying circles!”

“On the second flight on 21st and 22nd March, the auroral conditions weren’t as active early in the flight so we had to go further south to catch the active region of the aurora,” he said.  

Aurora events occur at Earth’s poles due to the interactions between the Sun and the planet's magnetic field, though aurora do not only occur here, with both Jupiter and Saturn (who have massive magnetic fields) also display them.

The phenomena are caused when particles stream off the Sun and eventually get caught in the Earth’s magnetic field, colliding with molecules in our atmosphere. These collisions cause the molecules to become excited and give off the display of colours that we see.

“The different colours come from different glowing gasses in the Earth’s atmosphere. Green is Oxygen and Red is Nitrogen,” said Ian, who is also an Honourary Research Fellow in Physics at the University of Otago.

“Incidentally the colours were hard to see with the naked eye. This is because to see colour the aurora has to be bright enough to stimulate the cone cells in your eyes. If the aurora isn’t bright enough to stimulate the cones you see it as a white/grey dynamic “mist” because the rod cells that are responsible for our low light vision can’t see colour.”

Due to the distribution of landmass around the geomagnetic poles, and more people living closer to the northern pole (as opposed to the southern pole), aurora are often witnessed in the northern hemisphere by many people, with annual images and videos flooding social media platforms of people catching them. 

However, here in the southern hemisphere, unless you are located in very southern regions, you have to go further south to see them. There are times of high solar and geomagnetic storm activity when the aurora can be visible as far north as New Zealand’ and Tasmania. At these locations, much like the north, the display of light and colour is visible from the ground.

“If the sun isn’t active, then Earth’s auroral oval retreats to the south and forms a narrow ring around the magnetic pole. If the sun is active, it stimulates the auroral oval which widens and moves northwards,” said Ian.

“I have personally seen the aurora australis from Wellington in New Zealand which is about 41 degrees south,” he said.

Typical auroras occur in oval bands that surround the poles of a planet that has a magnetic field and are likely seen during the night time from the ground. They can be seen out towards the horizon as sky glow (usually in bands of red or green) or directly above, like enormous moving curtains of light that wave back and forth in vertical columns within the atmosphere.

Dr. Michele Bannister, from the University of Canterbury, also got to take part in the flight experience, marvelling at seeing the interaction between the Earth and the Sun for the first time. 

“It was truly wonderful to get to see the aurora for the first time — seeing the curving curtains and ribbons of soft pale glow was magical. Seeing the conversation that happens in energy and light between the wind from the Sun and the field from the vast natural dynamo far below our feet, while flying in a way that felt like you were right up among the curtains, was fantastic.”

Humans have been looking up and wondering about the aurora for potentially tens of thousands of years, with Cro-Magnon cave paintings potentially showing the earliest depictions of them 30,000 years ago. There are also records from Chinese observers that have been documenting the events since the year 2600 BC, but the term “aurora” came from Galileo who named them after the Roman goddess of the morning, having mistaken them as sunlight reflecting from the atmosphere. 

Since then, scientists have worked out that the activity related to what we see in our skies is related to sunspots and the Sun’s 11-year cycle. The events have also increased our knowledge about our own planet’s magnetic field, and our atmosphere.

But aurora displays are not only just confined to Earth. The Gas Giants in our Solar system, Jupiter and Saturn give off magnificent aurora displays, some that are bigger in size than our entire planet. 

These are generated by the powerful magnetic fields both planets possess, created by their own liquid metallic cores. In Jupiter’s case, one of the Galilean moons - Io (which happens to be the most volcanic object in our entire system), supplies Jupiter’s powerful magnetic field with charged particles to create the light show on the giant planet. 

“Jupiter is a stand-out for its aurora - the strong magnetic field means it has some of the most spectacular aurora around, really loud in the radio,” said Dr. Bannister.

Aurora have also been observed on the comet 67P/Churyumov-Gerasimenko by the Rosetta spacecraft and were being produced by the accelerated electrons from the solar wind interacting with the comet’s tail - though, the processes of producing these were a little different from that of Earth and were detected in the far-ultraviolet wavelength range. 

The phenomenon has also been observed and documented by radio astronomers studying distant star systems that feature low-mass stars, or even their own planetary systems. The first of these was discovered in 2015, over the Brown Dwarf star known as LSR J1835+3259.

Joining the flight was Associate Professor Siouxsie Wiles from the University of Auckland who specialises in microbiology, who also experienced the southern lights for the first time.

“I had an amazing experience aboard the flight. I had the privilege of sitting next to Dr Stephen Voss who was one of the photographers on the flight so got to see what was going on outside the window not just by eye but through his camera lens too,” she said.

Setting the expectation, Dr Wiles also highlighted how the human eye perceives the aurora and in particular, the colours that are produced by them. 

“Though it's important for people to know that while they’ll be able to see the shapes made by the aurora, they might not be able to see the colours with the naked eye. To see the colours requires not just strong solar winds but also depends on the colour receptors in our eyes and these degrade as we get older,” she said. 

The flights have also been an opportunity for the lucky passengers to learn about the interplay between the Sun, and our planet’s atmosphere and magnetic field through a visual first-hand experience, as well as discussions with astronomers and astrophotographers. 

“I knew that auroras were caused by protons and electrons from the solar wind hitting particles in our atmosphere and releasing energy. But what I didn’t realise was that the colours are related to what particles in the atmosphere are being hit. The green of the aurora is caused by oxygen being hit and the red by nitrogen.”

Video Credits: Dr. Ian Griffin/Otago Museum.