Auroras and flares

It was too cold to photograph the aurora, but we
walked in snow, almost as bad for Australians

Having just returned from Norway after ticking off a bucket list item, seeing the Northern Lights we landed home to find the aurora's southern cousin was about. I pulled out some old notes: In 1716 Edmond Halley suggests that auroras are caused by “magnetic effluvia” moving along the Earth’s magnetic field lines. In fact, we now know better, thanks to a event in 1859, and here I pillage my history of 1859 science, Mr Darwin's Incredible Shrinking World.

Solar flares spout out from the Sun all the time, but at a distance, they are hard to detect, mainly because the Sun is so bright. Sometimes the flares are so massive that they still become apparent. A typical flare has the energy of a few million large hydrogen bombs, and it involves radiation right across the electromagnetic spectrum. In 1859, the known spectrum only extended from infrared, through visible and on to ultraviolet, and the astronomers could only see the visible part, but it was enough.

On September 1, 1859, two astronomers, Richard C. Carrington and Richard Hodgson, were independently  observing sunspots, using filters to limit the solar brightness, when they each detected a massive flare. The gamma rays, X-rays and other hard radiation travelled as quickly as the light, but a huge blast of protons crossed from the Sun at 8 million km/hr and slammed into the atmosphere, shredding the ozone layer, and setting off spectacular auroral displays, all over the world.

The ship Southern Cross left Boston on June 10 and arrived at San Francisco on October 22, a passage of 134 days. They were 23 days off Cape Horn, and that was where passengers and crew saw an amazing auroral display on September 2, thanks to a major solar storm. The storm was so violent that English astronomer Richard Carrington detected solar flares on the Sun, the first time they were seen.

Colourful auroras, usually only seen in polar regions, were visible at Rome and Hawaii. These were admired, but then the damage began. The storm sent a plasma blob hurtling out of the Sun, much faster than any cannon-ball, reaching the Earth in just under 18 hours. One day, another blob will come our way, but the damage next time will be far worse.

In 1859, telegraph wires suddenly shorted out across the United States and Europe, causing fires in many places, but it was comparatively minor damage. A modern solar blast like that of 1859 will cost billions of dollars as phone lines, power lines and communications satellites and earth stations are fried. Even computers and home networks could be at risk.

A couple of weeks after the flares, Scientific American reported that the current generated in the telegraph wires was enough to overcome the telegraph batteries, which in some cases were shut off, after which “ . . . messages were actually sent between Philadelphia and this city by the Aurora.” That is to say, the telegraph keys clattered aimlessly under the influence of stray currents induced in the lines.

The Scientific American reporter could see a hopeful aspect: if telegraph wires could scoop electricity out of the air, so, too, might balloons. What, asked the reporter, if balloons were able to collect and store the electricity and use it? (Scientific American, 17 September 1859, page 193.)

This sort of damage will come again: a 1989 solar flare caused surges that knocked out a Quebec power grid, and as our technology becomes more complex, there will be more lines, more circuits, more satellites and perhaps even more computers that are at risk. The next big flare will travel at the same speed, 5 million mph or 8 million km/hr, giving us about 19 hours to get ready. It won’t be a lot of time.