This is my review of Aurora: In Search of the Northern Lights by Dr Melanie Windridge.
Fascinated by the mysterious shape-shifting of the Northern Lights which intrigued both local communities and explorers long before they had an inkling of the scientific causes, plasma physicist Melanie Windridge set out to write a popular science-cum-travelogue to explain the phenomenon, visiting Sweden, Norway, Iceland, Canada and Scotland in the process.
The author makes comparisons to twanging elastic bands, strings of pearls or games of cricket to make theories easier to grasp. There is also a good deal of repetition, which can be useful, although I was left confused and frustrated by the fragmented explanation (with often unclear diagrams) of the all important “Dungey Cycle” by which the plasma stream of negatively charged particles from the solar wind interact with the earth’s magnetic field to give some of the most spectacular aurora effects on the night side of the earth. Perhaps I am puzzled over the above because the process is still not fully understood by the experts.
No doubt to achieve a reasonable length and to make the physics more digestible, the text sometimes seems “padded out” with mundane details of encounters, or over-long digressions into, say, the history of photography, but one cannot afford to skip anything. I found my interest unexpectedly caught by, for instance, the history of the Canadian town of Yellowknife, named after the copper blades of the knives carried by the local Dene people. In the series of prospecting rushes for minerals, the town had a belated gold mine open right up to 2003. For decades, the economy has functioned with “ice roads”, literally cleared of snow in order to freeze hard enough to support convoys of lorries, Now that the Canadian government is committed to the construction of the Mackenzie Valley Highway, there is local ambivalence over the inevitable damage to the ecosystem and traditional culture, the price to be paid for access to commercial progress. The focus on Yellowknife is of course due to its proximity to the Arctic Circle where the Northern Lights are most visible at night in the winter months.
Even if I am left unclear over the “aurora oval” and “reconnection”, I have certainly learned a good deal. Seen with the naked eye, the aurora may be much less impressive than the effect to be captured for the same event with a camera. Varying between arcs and “patchy pulsations”, the familiar green of the aurora derives from oxygen electrons which, with lower energy, may appear red: nitrogen molecules emit blue, violet and pink colours. Those who lived through the hundred year period from 1620 which became known as the Maunder Minimum would have seen few auroral displays, which seemed to coincide with a lack of sunspots visible on the surface of the sun. A “coronal mass ejection” or “vast blob of plasma” may be launched from the sun into space at great speed. Organisations like “Swipsie”, the Space Weather Prediction Center are co-operating to invest increasing resources in predicting whether it is likely to “interact with the solar wind ahead of it because this can twist up the magnetic fields and lead to a more severe event on earth”: apart from interference with the operation of satellites, this could involve damaging an electricity grid, or an unusually large and dramatic auroral display.