The Link Between Earth and Space

To the naked eye, Earth seems isolated from its celestial neighbors. Even the nearest of them, the Moon, is some 240,000 miles (386,000 km) away. Earth is anything but isolated, though.

Invisible to our eyes is an intricate system of interweaving magnetic field lines. They fuse, break and guide waves of charged particles and energy through space, sometimes creating just spectacular light shows around the poles, and other times disrupting our technology.

This system consists of three interacting parts:

1. The Solar Wind

Every second, the Sun spits out up to 1.9 million metric tons (1.9 billion kilograms) of charged particles in every direction, at astonishing speeds of 1 million mph (1.6 million kph). This is known as the solar wind. As this wind barrels into Earth's magnetic field, it flows around the planet to form a huge teardrop-shaped region known as Earth's magnetosphere. This is the part of space that is dominated by Earth's magnetic field.

2. Earth's Magnetosphere

Occasionally the solar wind pumps energy into Earth's magnetosphere, pulling it behind Earth like loading a slingshot. As more and more energy accumulates, the magnetosphere eventually releases the energy in an explosive event called magnetic reconnection. Energy and particles race down the magnetic field lines toward Earth's upper atmosphere, leading to heating, chemical changes and winds there. This release of energy brings the magnetosphere back to a more relaxed state.

3. Earth's Upper Atmosphere

As the energy and particles flow into Earth's upper atmosphere, it absorbs the energy and generates beautiful space weather phenomena, such as the dancing auroral light shows. But such space weather can also damage spacecraft, cause blackouts on Earth's surface, disrupt our everyday lives, and even jeopardize the safety of astronauts.

This flow of solar energy and particles in Earth's upper atmosphere creates 100,000-mile-long (161,000-kilometer-long) electrical circuits flowing along magnetic field lines. These currents form from complex processes in the magnetosphere, many of which scientists are still trying to understand.

A small but critical part of that circuitry are the auroral electrojets — electrical currents flowing high above Earth's poles.

By observing the electrojets' structure and evolution, scientists can resolve outstanding mysteries about what generates the circuit between Earth and space. The observations also help researchers build more accurate and powerful models to predict space weather events that affect our increasingly technological society.