How space weather powers auroras in the sky and threatens power grids on the ground
When an aurora lights up the sky, electric currents can also flow through the ground beneath your feet.
Northern lights, also known as auroras, are a captivating natural phenomenon characterized by colorful curtains that dance across the night sky. These mesmerizing displays are actually a result of space weather, a series of changes in Earth's environment triggered by solar activity. The sun's constant outpouring of charged particles and magnetic fields can give rise to these spectacular light shows, but they also carry potential threats to infrastructure on the ground, particularly power grids.
Space physicists study how these processes impact Earth's technological systems, as they have observed that a single space weather event, called a substorm, can trigger disturbances that manifest on Earth within mere minutes of occurring high up in the atmosphere. Substorms are triggered by the release of energy tens of thousands of miles away from Earth and can cause rapid fluctuations in the planet's magnetic field.
The journey begins with the solar wind, a stream of charged particles and magnetic fields emanating from the sun. When a coronal mass ejection (CME) erupts from the sun, this cloud of particles collides with Earth's magnetosphere, the magnetic shield that surrounds our planet. Depending on the orientation of the CME's magnetic field, it can connect with Earth's magnetic field on the sunward side, funneling the field lines outward into space behind the planet. This creates a vast region of stretched magnetic field lines called the magnetotail.
As the magnetotail continues to adjust to the incoming solar wind, the magnetic energy stored within it eventually reaches a critical point, and the field lines reconnect. This explosive process, termed a substorm, emanates from the night side of Earth, roughly 28,000 to 40,000 miles (45,000 to 65,000 kilometers) above the surface.
During this event, energetic particles flow along the reconfigured magnetic field lines towards Earth, colliding with oxygen and nitrogen molecules in the upper atmosphere at altitudes of 56 to 93 miles (90 to 150 kilometers).
These high-energy collisions produce the mesmerizing aurora, while the influx of particles also generates strong electrical currents in the upper atmosphere. Rapid changes in these currents can induce powerful electromagnetic forces in Earth's upper atmosphere and ground-level magnetic fields. These changes induce electric currents in power lines and transformers, potentially leading to damage, tripped circuit breakers, and even widespread power outages.
The impact of these disturbances varies across different regions, influenced by factors like local geology, soil composition, and atmospheric conductivity.
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