Over the course of the Sun’s 11-year solar cycle, the star goes through a period of increased and decreased activity. When this activity ramps up, sometimes phenomena such as solar flares and coronal mass ejections (CMEs), where massive amounts of radiation and solar particles erupt out from the Sun’s surface, can wreak havoc if our planet happens to be in the way of the blast.
The list below describes some of the more notable instances when this has occurred and their effects. NOAA studies the Sun so that we can better understand and forecast solar activity with the aim of mitigating potential issues like these in the future.
Astronomers Richard Carrington and Richard Hodgson independently observed patches of intensely bright light on the solar surface shortly before the Earth was hit by a very strong solar storm. The following day, strange things started happening; the northern lights were seen farther south than ever recorded before, and telegraph operators reported getting shocked by their equipment and seeing arcs of electricity sparking due to the powerful electric currents flowing through the wires.
Some reports mentioned telegraphs that were able to send messages without being plugged in and some that received nonsense messages that nobody had sent—because the atmosphere was so charged. Some telegraph stations that used chemicals to mark sheets reported that powerful surges caused the telegraph paper to combust.
Overall, this event caused widespread global outages and was determined to be the strongest flare to be observed in 500 years. It has come to be known as the Carrington Event.
A powerful solar storm almost caused the U.S. to go to war with the Soviet Union when a flare jammed several U.S. and United Kingdom radar and radio communications systems in polar regions at the height of the Cold War. Thinking it was the Soviets, the U.S. Air Force began preparing aircraft to fight, but luckily, military space weather forecasters intervened just in time, revealing that it was due to solar activity. The planes were not deployed and we avoided a potential nuclear weapon exchange.
Another large solar flare affected the Earth and Moon in August of 1972 between the Apollo 16 and 17 missions. According to NASA, television pictures kept breaking up due to solar activity, which later led to enormous solar flares. With no protective atmosphere on the Moon, it was lucky that no astronauts were in space or on the lunar surface at the time, else they could have suffered from severe radiation poisoning or worse. Thus, as we move into a future of increased human presence on the moon and in space, we will need the most accurate and timely space weather forecasts.
On the ground, the flares caused numerous radio blackouts and “spectacular aurora” bright enough to cast shadows from the United Kingdom to Bilboa, Spain, according to reports. Additionally, some of the U.S. military’s nuclear detection devices falsely suggested a nuclear bomb had detonated somewhere on the planet, and the solar activity likely caused several magnetic sea mines off the coast of Vietnam to explode.
Astronomers witnessed a powerful CME eruption on the Sun, and the associated flare that accompanied the outburst caused short-wave radio interference and jammed signals from Radio Free Europe, a U.S. government-funded organization that broadcasts uncensored news and information to audiences in countries where it is banned by the government. Some people even thought the signals had been jammed by the Kremlin.
By March 12, the cloud of solar plasma that reached Earth caused northern lights to be seen as far south as Florida and Cuba. It even created electrical currents in the ground beneath much of North America. On the morning of March 13, these currents affected a weak section of the electrical power grid in Quebec, Canada, and caused the entire city’s power grid to go down. The resulting blackout lasted for 12 hours, affecting millions of people. Other cities in the U.S. were also affected by the solar storm, where over 200 power grid problems erupted within minutes across the country. Luckily these did not cause additional blackouts.
The storm also affected various satellites in space and caused faulty sensor readings on the Space Shuttle Discovery, which went away once the solar storm subsided.
A large CME hit NASA’s Solar TErrestrial RElations Observatory (STEREO-A) satellite that orbits the Sun. The STEREO satellite was built to withstand these events, and based on the data collected, scientists realized that had the eruption occurred just one week earlier, Earth would have been in the line of fire.
"If it had hit, we would still be picking up the pieces," said Daniel Baker of the University of Colorado in a 2014 NASA statement. This statement also speculated that if a similar storm hit Earth today, it could have a catastrophic effect, with a total economic impact exceeding $2 trillion or 20 times greater than the costs of Hurricane Katrina. Multi-ton transformers damaged by such a storm might take years to repair. Unlike the Carrington Event, we are now much more reliant on technology than in the 1850s.