From time to time, the sun discharges billions of tons of solar matter, traveling millions of miles per hour, straight at Earth.
Yet humans and life on the surface aren't physically harmed by the intense space radiation. That's why, when the strongest solar impact to occur in over 20 years recently hit, you may have been blithely unaware — except for the resulting atmospheric light show, as magnificent glowing auroras appeared in unusual places.
Not all worlds, like the moon and Mars, have such protection. Yet Earth boasts both a robust magnetic field and atmosphere, which keep dangerous cosmic particles away from our fragile flesh.
"Without those we would be in real trouble," Bennett Maruca, an assistant professor of physics and astronomy at the University of Delaware who researches the sun, told Mashable.
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Earth's protective magnetic field
Some 1,800 miles beneath your feet lies a giant, blazing-hot ball of metal.
Earth's core is largely made of molten iron and nickel — an ideal fluid to conduct electricity. As it swirls around and around it acts similar to an electric generator, creating electrical currents that naturally produce a big magnetic field. As the graphic below shows, the magnetic field loops out from the poles, trapping harmful solar energy a safe distance away (and in some cases deflecting these energetic solar particles).
Ultimately, many particles slam into Earth's atmosphere, following magnetic lines to the poles where they deposit energy and produce fantastic atmospheric radiance (popularly called the Northern Lights in the Northern Hemisphere).
The instigators of the recent lights were "coronal mass ejections," or CMEs, from the sun. These are great masses of hot gas (plasma), essentially a chunk of the sun, hurled into space. When they collide with Earth, they can create robust "geomagnetic storms," which are disturbances in Earth's magnetic field from these solar shocks.
"Multiple coronal mass ejections from the sun sparked an extreme geomagnetic storm around the Earth last week [May 11], creating stunning auroras, even in places where the northern lights are rarely seen," the National Oceanic and Atmospheric Administration explained. "The Southern Hemisphere also reported remarkable auroras from the storm."
Earth's protective atmosphere
Our planet's upper atmosphere also shields us from harmful solar activity, not just coronal mass ejections, but also the relentless solar wind and solar flares (explosions of light from the sun's surface).
"It's a planetary kevlar vest," Maruca emphasized.
Well above our clouds and weather, both the ionosphere and thermosphere (together ranging from some 50 to 400 miles up) absorb charged particles and damaging radiation, like X-rays and UV rays.
"We're well-protected by the natural systems here."
"We're well-protected by the natural systems here," Andrew Layden, chair of the Department of Physics and Astronomy at Bowling Green State University, told Mashable.
Of course, astronauts on the International Space Station (and in the coming years on the moon or Mars) aren't protected by these natural buffers; hence the extra shielding on the station. Airline workers, working at higher altitudes, may potentially have some exposure risk, too, though this is an ongoing area of research.
The dangers to our technology
Extreme eruptions from the sun, located 93 million miles away, can't physically hurt us. But our electrical and communication systems are vulnerable. "It's not our biological systems at risk – it's our technology," Maruca said.
During the May 2024 solar storms, many farming tractors, reliant on GPS satellite guidance systems, went offline. In 2003, airlines rerouted flights, at great cost, to avoid communication blackouts. In 1989, an extreme solar storm fried a $10 million transformer at Salem Nuclear Power Plant in New Jersey. The same CME knocked out power to millions in Québec, Canada. It hit Earth's magnetic field, and then, wrote NASA astronomer Sten Odenwald, "Just after 2:44 a.m. on March 13, the currents found a weakness in the electrical power grid of Quebec. In less than two minutes, the entire Quebec power grid lost power. During the 12-hour blackout that followed, millions of people suddenly found themselves in dark office buildings and underground pedestrian tunnels, and in stalled elevators."
Even bigger solar storms are inevitable.
The largest such episode ever observed was the Carrington Event, in 1859, The solar storms produced auroras so bright, they awoke Rocky Mountain gold miners at 1 a.m., and people could reportedly read newspapers by the eerie atmospheric light.
Such an event today — if not properly prepared for — could stoke widespread electrical blackouts and fry communications satellites. "If that were to occur today it would do a lot of damage," Layden said. "No one knows when that Carrington-level event is going to happen again." A report from the National Academies says that an estimate of "$1 trillion to $2 trillion during the first year alone was given for the societal and economic costs of a 'severe geomagnetic storm scenario' with recovery times of 4 to 10 years."
"It's a staggering figure," Maruca said.
Thankfully, we have space weather prediction experts, such as those at NOAA, who can provide warning of an incoming blast of charged particles and radiation. Power utilities, for example, can temporarily shut down electric grids to avoid permanently-damaged infrastructure.
It's only a matter of time. "Investing in space weather prediction is a good thing to do," Layden said.
Topics NASA