What Is a G5 Storm?

One of the most powerful—and potentially damaging—space weather phenomena are G5 storms. But what exactly is a G5 storm and what kind of effects can it have on Earth?

Space weather is a term used to describe the phenomena that occur in the space environment between the sun, Earth and beyond. It originates from solar activity and can manifest itself in various different ways, including solar flares, coronal mass ejections and geomagnetic storms, among many others.

While the Earth's magnetic field largely protects us from charged particles emitted by the sun, space weather phenomena can sometimes have an impact on our planet, interfering with life and technological infrastructure, both in space and on the ground.

What Is a Geomagnetic Storm?

Geomagnetic storms are significant disturbances in the Earth's magnetic field caused by changes in the solar wind—a stream of energized, charged particles that flow out of the sun—and the interplanetary magnetic field.

Variations in the solar wind can affect the nature of the Earth's magnetic field, resulting in geomagnetic storms that can last anywhere from hours to days.

The solar wind interacting with Earth
Stock image: An artist's illustration of solar interacting with the Earth's magnetic field. Geomagnetic storms are major disturbances in the Earth’s magnetic field caused by changes in the solar wind. iStock

These storms are often caused by coronal mass ejections (CME)—large expulsions of plasma (the fourth fundamental state of matter) and magnetic field from the outermost part of the sun's atmosphere, called the corona.

High-speed streams of solar wind can also result in geomagnetic storms, although these events tend to be less intense than those associated with CMEs.

What Are the Effects of a Geomagnetic Storm?

Geomagnetic storms heat and distort the ionosphere—part of the Earth's upper atmosphere beginning at around 50 miles above sea level. This can cause interference with long-range radio communication as well as global-positioning systems (GPS).

These storms can also damage satellite electronics. And on the ground, these events can result in power grid surges, which can lead to blackouts.

What Is a G5 storm?

The National Oceanic Administration (NOAA) has created a measurement system to grade geomagnetic storms and their potential effects ranging from G1 (minor) to G5 (extreme).

"Essentially, think of it as a scale for how strong the storm is likely to be," Piyush Mehta, an assistant professor of mechanical and aerospace engineering at West Virginia University, told Newsweek.

"G5 is likely going to impact anything and everything we know about what space weather impacts currently," he said.

While minor geomagnetic storms are likely to have very little effect on the Earth, one that is classified as G5 could produce potentially devastating impacts.

For example, some power grid systems could completely collapse causing widespread outages. Meanwhile, satellite navigation systems might experience difficulties for days. In addition, aurorae might be visible from regions as far south as Florida and southern Texas, according to the NOAA.

Thankfully, G5 storms are rare, but when they do occur, they have the potential to cause serious damage. The strongest geomagnetic storm on record was the Carrington Event of 1859, which led to the failure of telegraph systems around the world, even sparking fires in some telegraph stations.

Aurora Borealis in Iceland
Stock image: Aurora Borealis in the night sky above Iceland. Geomagnetic storms can trigger an aurora in places the phenomenon is not normally seen.

"When it happened, we didn't really have a lot of technology infrastructure," Mehta said. "We only had telegraph lines and things like that, we didn't have power lines. So, it is estimated that a repeat of a Carrington Event today could cause damage worth $2 trillion."

"There are different models that have been developed to predict how likely or how often such events are likely to occur," he said. "And most of the models suggest that a Carrington-type event will likely occur every few hundred years. Nobody really knows exactly when it's going to happen. So, it is better to be prepared and improve our ability to predict when it's going to happen."

According to Mehta, there is also the possibility that storms stronger than the Carrington Event could occur one day.

"There is always the unknown. We just don't know how strong the storm can actually get," he said.

While predicting when a geomagnetic storm will occur is difficult, they are more likely to occur close to a solar maximum—a period in the sun's 11-year cycle when it is particularly active.