Beware ‘Head-On’ Aurora Displays Say Scientists

“Interplanetary shocks” that hit Earth’s magnetic field head-on are what scientists need to forecast to protect any infrastructure that conducts electricity, according to a new study published today in Frontiers in Astronomy and Space Sciences.

The appearance of magnificent displays of green, red, purple and blue aurora—such as the global geomagnetic storm on May 10—can mean the arrival at Earth of strong currents that can potentially damage power transmission lines, oil and gas pipelines, railways and submarine cables.

Interplanetary Shocks

An interplanetary shock—which can lead to sightings of the beautiful Northern Lights and Southern Lights—is a disruption in the solar wind. It’s caused by coronal mass ejections from the sun. A CME is a cloud of magnetic fields and charged particles from the sun that streams into space at up to 1,900 miles (3,000 kilometers) per second.

The disturbance causes Earth’s protective magnetic bubble to compress, often triggering aurora. However, it’s the impact angle of interplanetary shocks that is key to the strength of the currents, says the research.

It’s important because interplanetary shocks are much more common during solar maximum, which scientists think is occurring now.

Geomagnetically induced currents can damage infrastructure that conducts electricity. The more powerful an interplanetary shock, the more powerful currents and auroras. If scientists can predict that an incoming interplanetary shock is going to be head-on, rather than a glancing blow, that will help protect infrastructure before the strike, say the researchers.

Higher Peaks

The paper found that shocks that hit the Earth head-on, rather than at an angle, induce the strongest geomagnetically induced currents. Using a database of interplanetary shocks and cross-referencing it with readings of geomagnetically induced currents from a natural gas pipeline in Mäntsälä, Finland—in the “aurora zone”—the scientists found that frontal shocks cause higher peaks in geomagnetically induced currents. That’s because they compress the magnetic field more.

They also found that the most intense peaks occurred around “magnetic midnight,” the time of night (around actual midnight, local time) when the north pole was between the sun and Mäntsälä on Earth’s night side.

Space Weather

“Auroras and geomagnetically induced currents are caused by similar space weather drivers,” said Dr Denny Oliveira of NASA’s Goddard Space Flight Center, the lead author. Space weather is the flow of charged particles from the sun—the solar wind. “The aurora is a visual warning that indicates that electric currents in space can generate these geomagnetically induced currents on the ground.”

The display of aurora on May 10 was particularly intense. Aurora appears as an oval around the polar regions, but on that date, the arrival of several CMEs caused the oval to expand. “The auroral region can greatly expand during severe geomagnetic storms,” said Oliveira. “Usually, its southernmost boundary is around latitudes of 70 degrees, but during extreme events, it can go down to 40 degrees or even further, which certainly occurred during the May 2024 storm — the most severe storm in the past two decades.”

Wishing you clear skies and wide eyes.

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