[Sunspots sketched by Richard Carrington on Sept. 1, 1859. Copyright: Royal Astronomical Society]
It was this time of year 155 years ago when the solar superstorm, now known as the Carrington Event, took place during solar cycle 10. The event has been named for the British astronomer, Richard Carrington, as he observed from his own private observatory the largest solar flare during this event which caused a major coronal mass ejection (CME) to travel directly toward Earth. The 33-year-old astronomer - widely acknowledged at the time to be England’s best - also recorded in detailed fashion the appearance of the sunspot regions that he saw at the time.
From August 28, 1859 to September 2, 1859 numerous sunspots and solar flares were observed on the sun and auroras were being observed in different parts of the world. Just before noon on September 1st, Richard Carrington was using his telescope to project an 11-inch wide image of the sun on a screen and he carefully drew the sunspots that he saw. Suddenly, two brilliant beads of blinding white light appeared over the sunspots and he realized that he was witnessing something unprecedented. He left for about one minute to find another witness and found upon their return that much had already subsided.
Just before dawn the next day, skies all over Earth erupted in red, green and purple auroras - even in tropical locations like Cuba, the Bahamas and Hawaii. The massive solar flare caused a major CME that reached the Earth some 17.6 hours later. Normally such a journey takes 3 or 4 days, but an earlier CME actually cleared the way of the ambient solar plasma for the second blast to move so quickly. The auroras were so bright over the Rocky Mountains that their glow awoke gold miners who began preparing breakfast because they thought it was morning. People in the northeastern US could read a newspaper by the aurora’s light. Telegraph systems all over Europe and North America went haywire and, in some cases, telegraph operators were literally shocked as sparks were flying and telegraph paper was often set on fire. Some systems continued to work despite being disconnected from their power supplies as aurora-induced electric currents still allowed messages to be transmitted.
Now we know that solar flares happen frequently, especially during solar sunspot maximums, but in those days there were no X-ray satellites or radio telescopes and no one knew flares existed until that September morning. “It is rare that one can actually see the brightening of the solar surface which takes a lot of energy to heat up the surface of the sun” says a modern day NASA astronomer. “In the 160-year record of geomagnetic storms, the Carrington event is the biggest.” In fact, going back farther in time by examining Arctic ice (energetic particles leave nitrates in ice cores), it is estimated that this event may have been the biggest in 500 years and nearly twice as big as the runner-up.
In today’s world, electronic technologies have become embedded into everyday life and are, of course, quite vulnerable to solar activity. Power lines, long-distance telephone cables, radar, cell phones, GPS, satellites – all could be significantly affected by an event like this one. The good news is that observations of the sun are a constant in today’s world with a fleet of spacecraft in position to monitor the sun and gather data on solar flares. The bad news is that the Carrington Event occurred during a weak solar cycle (10) which actually resembles rather closely our current solar cycle (24) so we always have to stay on guard for a potential powerful solar storm - even during times of weak solar cycles.