Space Plasma: The Invisible Force Powering Auroras

By the end of this article, you will understand how invisible clouds of solar plasma crash into Earth’s magnetic shield to create breathtaking auroras and dangerous space weather.

Before rockets and satellites, scientists didn’t know space weather existed. Then came the Carrington Event of 1859. Astronomer Richard Carrington saw a massive solar flare erupt on the Sun. Just 17 hours later, the Earth was slammed by a geomagnetic storm. It was a Surprise: auroras were seen as far south as the Caribbean, and telegraph systems—the high technology of the day—went completely haywire, sparking fires and shocking operators! This proved that the Sun and Earth are deeply connected by invisible forces. We now know this was caused by a Coronal Mass Ejection (CME)—a massive cloud of electrified gas called plasma, hurled through space.

Original Review Paper: ‘Space Plasma Physics: A Review’ by Tsurutani et al.

One swallow does not make a summer, but Carrington’s flare sparked the largest magnetic storm in 200 years.
— Historical context by Richard Carrington (paraphrased)

This is NOT the plasma found in your blood! In space physics, plasma is the fourth state of matter. If you heat a gas enough, its atoms break apart into a soup of negatively charged electrons and positively charged ions. Because they have an electrical charge, plasmas are pushed and pulled by magnetic fields. The Sun is basically a giant ball of plasma. It constantly breathes out a ‘solar wind’ that fills the entire solar system. When this solar wind carries a tangled magnetic field that crashes into Earth’s own magnetic bubble (the magnetosphere), the two fields can link up. This process, called magnetic reconnection, acts like a slingshot, releasing massive amounts of stored energy.

When solar wind energy builds up in the long ‘tail’ of Earth’s magnetic field on the night side, the field lines stretch until they break and reconnect. This magnetic slingshot fires high-energy electrons down into Earth’s upper atmosphere. When these electrons smash into oxygen and nitrogen atoms, they glow, creating the beautiful light shows we call auroras! But there is a dark side: this exact same process creates Geomagnetically Induced Currents (GICs). These invisible currents can flow through the ground and blow up power grid transformers, proving that auroras are the beautiful warning signs of dangerous space weather.

Because of the bloody color of SAR arcs, red auroras have been omens for war and bloodshed in ancient times.
— Dr. Bruce T. Tsurutani & Team

How do scientists study things they can’t even see? It requires incredible Knowledge and Tools. Today, researchers use fleets of satellites, like the Van Allen Probes and Voyager missions, packed with miniaturized instruments to measure the speed, density, and magnetic direction of plasma in space. They look for ‘whistler mode chorus waves’—electromagnetic waves that sound like chirping birds when converted to audio. By analyzing these waves, scientists can predict how ‘killer electrons’ will behave during a storm, helping us protect the satellites that run our GPS and communication networks.

Measurements of magnetic pulsations can be utilized for geophysical surveys to probe the subsurface conductivity structure of the Earth.
— Space Plasma Researchers

Q: If a massive solar storm hit today, what would happen?
A: Because we rely heavily on electricity and satellites, a massive storm could cause widespread power blackouts, disable GPS navigation, and disrupt global communications for days or even months.