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Physics Lecture Searches for Northern Lights

Wednesday, 09 November 2016

Dr Melanie Windridge continued the Girls’ Division’s series of Science and Arts lectures with a fascinating talk about the physics of the aurora, or northern and southern lights. Speaking to an audience of pupils, staff and members of the public, she discussed her personal journey in researching this fascinating phenomenon. Her work on the aurora has taken her across Scandinavia, to Canada and even to Svalbard, one of the world’s northernmost inhabited areas.

Her first trip into the auroral zone was to Sweden, and she shared a picture from her first glimpse of the aurora, taken during this trip. She then visited Norway, where she stayed near Haldde Mountain, the place where the physicist Kristian Birkeland created a permanent monitoring station to study the aurora and came up with the first plausible theory for what caused these lights in the sky.

Birkeland’s theory was that charged particles from the sun travelling down geomagnetic field lines were behind the aurora. However his explanation, like many others, was incomplete. Dr Windridge gave a clear and captivating description of substorms, which cause the particles to accelerate, giving them the energy to create the global phenomenon that is the aurora. Dipping into atomic physics, Dr Windridge also explained how the electrons transitioning between different energy levels within atoms is what causes the spectacular displays of light.

During her time in Canada, she was able to visit All-Sky Cameras which can view the sky from horizon to horizon. She showed a breathtaking composite photograph of the auroral display across the breadth of country, proving that the aurora happens everywhere on the planet at once.

However, she also warned that pictures of the aurora do not always show what the naked eye can see. She showed a surprising side-by-side comparison of what is visible next to what a camera can photograph, with the photo showing much brighter colours and clearer shapes. Nonetheless, she stressed that seeing the northern lights is still an incredible experience, even if they don’t look exactly like the pictures.

Moving away from the fascinating colours and displays of light, Dr Windridge talked about some of the problems that are caused by the aurora. The charged particles that create the aurora can also disrupt radio signals and GPS, do damage to satellites, induce currents in conductors, and create many more problems. She therefore talked about the importance of forecasting space weather so that these issues can be avoided where possible. Scientists at NASA and the Met Office are studying and monitoring space weather much more closely now so that they can issue alerts: these simultaneously help to prevent disruptions for airline operators, power companies and others who are affected by the negative effects of charged particle, and assist aurora spotters with knowing when is a good time to look for the northern or southern lights.

Nearing the end of her journey, Dr Windridge decided that she wanted to see the aurora as the old polar explorers once did, and so she decided to travel to Svalbard and ski across the ice there. She talked about the experience of travelling there in February and skiing in constant twilight and darkness. She brought with her a video clip to prove that the peaceful image from her photographs was an illusion, due to the sound of skis on ice. She said, “We progressed in our own little world – we couldn’t even talk, it was too loud!” She added, “You become really, really focused. You can only concentrate on what absolutely has to be done. It’s almost like you don’t have any space in your head for anything that’s frivolous or emotional, because you have to just keep focused on keeping warm, skiing, eating, drinking and these are the things that matter.”

She described the many difficulties faced in such a harsh and unforgiving environment, and finally showed an image of the aurora that she saw on Svalbard. She concluded her polar adventures with the experience of watching a total solar eclipse while still in Svalbard a few weeks later.

In addition to the science, throughout her talk Dr Windridge talked about the spiritual and religious connections that have been made to the aurora, citing biblical passages and accounts from the assassination of Julius Caesar and the American Civil War that seem to describe a red auroral display in the sky. She also mentioned the folklore and superstitions that she discovered in Scandinavian countries, where the displays are more green and blue in colour, and the way people explained the lights as spirits or icy reflections. She also touched on the lasting cultural influence of the aurora, which has given its name to everything from a type of beer to a Canadian Air Force aeroplane.

She concluded her talk by saying that the aurora is the Earth’s connection to the sun, and the planet’s way of protecting itself is through producing this incredible light show.

The evening ended with questions from the interested audience. Dr Windridge discussed the colours of the aurora and why red tones are more common further south: the colour red is often only produced at high altitudes, and because of the curvature of the Earth, people in the south often cannot see the green part of the aurora below as it’s blocked by the planet. She was also asked about auroras on other planets and said that it is likely, if the planet has both an atmosphere and a magnetic field. However, Jupiter’s aurora may be generated differently due to interaction with its volcanic moon.

After the talk, Dr Windridge signed copies of her book Aurora: In Search of the Northern Lights for members of the audience.

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Dr Windridge with some of the pupils who attended her talk

Dr Windridge with some of the pupils who attended her talk

Explaining how the aurora is created in the Earth

Explaining how the aurora is created in the Earth's magnetosphere

The aurora viewed as a global phenomenon

The aurora viewed as a global phenomenon