That recent solar storm was detected nearly two miles beneath the ocean

On May 10, 2024, people across North America were treated to a rare celestial event: an aurora visible from the East Coast to the southern United States. This particular sighting of the Northern Lights (also known as Aurora Borealis) coincided with the the most extreme geomagnetic storm since 2003 and the 27th strongest solar flare ever recorded. This led to the dazzling display that was visible to residents across North America, but was also detected by some Ocean Networks Canada (ONC) undersea sensors at a depth of almost three kilometers.

An initiative of the University of Victoria, supported by the Government of Canada, ONC is one of the country’s premier research facilities. The network includes wired observatories along Canada’s Pacific, Atlantic and Arctic coasts and the Southern Ocean. that provide continuous power and internet to scientific instruments, cameras and more than 12,000 ocean sensors. According to a May 15 statement, ONC instrument platforms on Canada’s west and east coasts recorded the temporary deformation of Earth’s magnetic field at depths up to 2.7 km (1.68 miles) below the ocean.

Ocean Networks Canada infrastructure map. ONC operates leading observatories in the deep ocean, coastal waters and land of Canada’s Pacific, Atlantic and Arctic coasts and the Southern Ocean. Credit: UVic/ONc

The disturbances caused the movement of compasses, which the ONC uses to orient its Acoustic Doppler Current Profilers (ADCP) instruments that measure ocean currents. The main magnetic shift was detected by the wired ONC NEPTUNE observatory off the coast of Vancouver Island. A compass from this observatory, at a depth of 25 meters (82 ft) at the Folger Passage location, shifted within a range of +30 to -30 degrees. These magnetic disturbances were discovered during data quality checks, which the ONC routinely performs to ensure their sensors are working.

ONC data specialist Alex Slonimer was doing a daily check on the Ocean 3.0 data portal in late March when he first noticed the anomaly. Last week’s much larger solar storm reinforced this observation. Slonimer noted that the peaks in the compass directions were closely correlated with the peaks in the visible activity in the aurora. “I looked into whether it was possibly an earthquake, but that was incorrect because the changes in the data lasted too long and occurred at the same time in different locations,” Slonimer said in a UVic News release. “Then I checked to see if it was a solar flare, since the sun has been active recently.”

Professor Justin Albert from UVic’s Department of Physics and Astronomy welcomes this news and sees great potential for undersea detection of solar storms:

“The next two years will be the peak of the eleven-year solar cycle. After a decade of relative inactivity, auroral events like this past weekend are likely to become more common in the coming years, although the Sun’s variability makes accurate prediction of such events impossible. ONC’s network could provide very useful additional insight into the effects of solar activity on Earth’s geomagnetism.”

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