Northern lights caused by head-on impacts to Earth’s magnetic field could damage critical infrastructure, scientists say

The northern lights have inspired myths and omens for millennia, but only now, thanks to modern technology that relies on electricity, are we appreciating their true power. The same forces that cause the northern lights also cause currents that can damage infrastructure that carries electricity, such as pipelines.

Now scientists write in Frontiers of Astronomy and Space Science demonstrated that the impact angle of interplanetary shocks is critical to the strength of the currents, providing the opportunity to predict dangerous shocks and protect critical infrastructure.

“Aurorae and geomagnetically induced currents are caused by similar space weather factors,” said Dr. Denny Oliveira of NASA’s Goddard Space Flight Center, lead author of the paper. “The aurora is a visual warning that electrical currents in space can generate these geomagnetically induced currents on the ground.”

“The auroral region can expand considerably during strong geomagnetic storms,” he added. “Usually its southernmost limit is around latitudes of 70 degrees, but during extreme events it can extend down to 40 degrees or even further, which is certainly what happened during the May 2024 storm, the strongest storm in the last two decades.”

Lights, colors, action

The northern lights are caused by two processes: either particles ejected from the Sun reach the Earth’s magnetic field and cause a geomagnetic storm, or interplanetary shocks compress the Earth’s magnetic field.

These tremors also generate magnetically induced currents, which can damage electrically conductive infrastructure. More powerful interplanetary tremors cause more powerful currents and auroras, but less powerful and more frequent tremors can also cause damage.

“It can be said that the most intense deleterious effects on electrical infrastructure occurred in March 1989, following a violent geomagnetic storm: the Hydro-Québec network in Canada was shut down for almost nine hours, leaving millions of people without electricity,” Oliveira said.

“But smaller, more frequent events, such as interplanetary collisions, can pose a threat to Earth’s conductors over time. Our work shows that large geoelectric currents occur quite frequently after collisions, and they deserve attention.”

Shocks that hit the Earth head-on, rather than at an angle, are thought to induce stronger geomagnetic currents because they compress the magnetic field more. Scientists have studied how geomagnetic currents are affected by shocks at different angles and at different times of day.

To do this, they took a database of interplanetary shocks and cross-referenced it with readings of geomagnetically induced currents from a gas pipeline in Mäntsälä, Finland, which is typically in the auroral region during active periods.

To calculate the properties of these shocks, such as angle and speed, they used data from the interplanetary magnetic field and the solar wind. The shocks were divided into three groups: highly inclined shocks, moderately inclined shocks, and near-head-on shocks.

Angle of attack

They found that more frontal shocks cause higher peaks in geomagnetically induced currents, both immediately after the shock and during the following substorm. Particularly intense peaks occurred around magnetic midnight, when the North Pole was between the Sun and Mäntsälä. Localized substorms at this time also cause striking auroral brightening.

“Moderate currents occur shortly after the disturbance hits when Mäntsälä is around dusk local time, while more intense currents occur around midnight local time,” Oliveira said.

Because the angles of these shocks can be predicted up to two hours before impact, this information could allow us to put protections in place for power grids and other vulnerable infrastructure before the strongest, most frontal shocks occur.

“Electrical infrastructure operators could take measures to protect their equipment, such as managing a few specific electrical circuits when a shock alert is issued,” Oliveira suggested. “This would prevent magnetic field-induced currents from reducing the equipment’s lifespan.”

However, the scientists did not find strong correlations between the angle of a shock and the time it takes for it to strike and then induce a current. This may be because more recordings of currents at different latitudes are needed to study this aspect.

“The current data was only collected at one particular location, namely the Mäntsälä gas pipeline system,” Oliveira warned.

“Although Mäntsälä is located in a critical location, it does not provide a global overview. In addition, the Mäntsälä data are missing several days in the studied period, which forced us to exclude many events from our shock database. It would be nice if energy companies around the world would make their data available to scientists for study.”