The Auroral Electrojets

Earth's auroral electrojets are electrical currents traveling around the planet's magnetic poles. From roughly 65 miles (100 km) above the surface, the electrojets push roughly 1 million amps of electrical charge around the poles every second, making them responsible for some of the largest magnetic disturbances on the ground.

The Substorm Current Wedge

The auroral electrojets are just a small part of a vast electrical circuit flowing between the magnetosphere and Earth's upper atmosphere. When drawn, the circuit resembles an enormous wedge-like structure, which scientists aptly call the substorm current wedge. The illustration to the right depicts the wedge-like system that flows into the North Pole; another unillustrated one flows into the South Pole.

These structures are essentially massive power cords, stretching over 100,000 miles (160,000 km) between Earth's ionosphere and its magnetosphere.

The Auroral Electrojets

Although they're just a small portion of the huge wedge-like system, the auroral electrojets produce a strong magnetic field that scientists can use to monitor how the entire wedge-like system behaves.

What's the Big Question EZIE Is Addressing?

Scientists have measured the electrojets' magnetic field for more than a century with ground-based magnetometers. They know it's fundamental to understanding the wedge system and how the magnetosphere releases energy.

But they're still debating what the overall system looks like and how it evolves.

The depiction to the right, for example, is just one idea of how the auroral electrojet and the wedge system would appear if they were visible.

In the nearly 50 years since the substorm current wedge model was published, teams have proposed a steady stream of new but conflicting models of the current wedge system. These generally fall into three structures:

1. A single wedge system, as we've been showing.

2. Two wedges with opposite flows.

3. Two overlapping wedges.

EZIE's aim is to test which — if any — proposed structure is correct. By flying through the midnight region of the auroral electrojets, the mission will not only resolve decades of controversy but, perhaps more importantly, provide insight into the physics of our magnetosphere — knowledge that would apply to any magnetized planet in the universe.