Solar activity drives both visible auroras in the night sky and invisible underground electric currents that can disrupt power grids, satellites, and GPS networks within minutes of a magnetic energy release tens of thousands of miles away in space.
How Solar Storms Trigger Substorms
Occasionally, the Sun releases a much larger eruption called a coronal mass ejection. When this cloud of charged particles and magnetic fields reaches Earth, it interacts with the planet’s magnetosphere. If the magnetic field of the coronal mass ejection is oriented in a certain way, it connects with Earth’s magnetic field on the sunlit side. The solar wind then carries these connected field lines around Earth and stretches them far out into space behind the planet, forming a long region called the magnetotail.
Magnetic energy builds up in the magnetotail until the field lines come close enough to reconnect. This stored energy is released in an explosive process known as a substorm, which occurs on the nightside of Earth roughly 28,000 to 40,000 miles (45,000 to 65,000 kilometers) away. During the substorm, energetic particles shoot along magnetic field lines toward Earth, colliding with oxygen and nitrogen atoms in the upper atmosphere about 56 to 93 miles (90 to 150 kilometers) overhead to produce the glowing aurora.
Measuring Ground Impacts of Substorms
Space physicists studying these events combined data from NASA spacecraft—including THEMIS and NOAA’s GOES satellites—with ground observations from a network of magnetometers across Arctic Canada. About seven minutes later, the magnetic field at the ground began to change rapidly. These ground disturbances began at lower latitudes and spread toward the North Pole over the next 20 to 30 minutes.
Nearby geomagnetic stations often recorded very different responses, with stations tens to hundreds of miles apart seeing strong magnetic swings at one site and weak ones at another. This variation depended on the strength of upper-atmosphere electrical currents and local conditions, including the electrical conductivity of the upper atmosphere and the local geology and moisture levels of the ground beneath the station.
Historical Disruption of Power Grids
A paper from Acrisure Re produced in cooperation with ETH Zurich noted that the 1989 Quebec event knocked the James Bay power network offline in under 90 seconds at a magnetic field intensity of approximately -589 nT.
A similar combination occurred during the Halloween storms of October 2003, when auroras illuminated skies across Europe and geomagnetically induced currents contributed to a blackout affecting about 50,000 people in Malmö, Sweden.
Financial Losses From Future Storms
Estimates for a repeat of the 1989 Quebec event range widely.
That study estimated blackouts would last at least 72 hours in three large and six medium-sized European Union cities, with total EU losses reaching 13.2 billion euros ($14.8 billion).
Orbital Exposure of Satellites and GPS
Active satellites rose from 1,980 in 2018 to 16,393 as of August 2026, according to Mission Space research cited in the Acrisure Re report, as the orbital economy’s exposure expanded sharply alongside satellite infrastructure growth.
Sensors Monitoring Space Weather
To better monitor Earth’s atmosphere and study geomagnetic storms, the European Space Agency has developed space weather missions under its Space Safety programme named Aurora, Swing, and Sawa. The Aurora mission patrols the north and south poles to monitor the impact of space weather, Swing focuses on the ionosphere to track disruptions to radio signals and satellite navigation, and Sawa studies the thermosphere as heating causes it to expand and push satellites off course. Data from these missions feed into forecasts and alerts designed to help industries such as aviation, satellite navigation, and power grids brace for impact.