150 years on, a solar flare from history…

On the first of September 1859, the Earth was struck by an enormous solar flare. Coincidentally, English Astronomer Richard Carrington was sketching a sunspot just before this event and saw the flare coming – the first ever recorded as being observed from the Earth. As it hit, it induced currents in every wire in the new telegraph system below. These currents overloaded some batteries and enabled some other telegraph wires to be run on the power supplied by the bright aurorae above.

Now these types of aurorae aren’t the nice fluffy ones we see in photographs taken at the arctic. Those ones are mostly caused by particles trapped inside the Earth’s magnetic field being released by acceleration processes that derive their energy from the passing solar wind. The solar wind that hits the Earth dead on is mostly deflected away by the magnetic field, but the highest energy fraction does make it down, channeled to the poles to create a low energy ‘cusp aurora’, normally of only academic interest. If the high energy part of the solar wind is increased, by a flare or coronal mass ejection, then this dot grows and the cusp aurora is seen at lower latitudes across the globe as evidence of the massive impact of solar particles.

Aurorae create a lot of havoc. The increased ionisation interferes with radio communications. Wires on the ground have currents induced in them – more wires means more induced current and so more power overloading the transformers and generators. We’ve grown since 1859 in terms of the numbers of wires we have about the place and have suffered for it when small flares came along, disrupting air traffic, knocking out satellites and closing down substations.

Although the 1859 flare was a once in five hundred year event, moderate flares are far more frequent. One good reason why the recent destruction of the UK’s solar terrestrial research capacities by the Science and Technology Facilities Council was a short sighted act, just as the parliamentary committee that looked into it described it, the act was “bizarre”.


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