#substorm

Electrojet

This photo was taken in March of 2015 during one of the 2 largest geomagnetic storms of the last solar cycle. These events triggered large aurora outbreaks and, in the right spots, they were actually strong enough to trigger electrical currents at the planet’s surface. Currents traveling at the planet’s surface can move in things humans build, including electrical systems, telecommunications wires, and even gas and oil pipelines.

If these currents are strong enough, they can actually damage those systems. In the middle of the 19th century, a famous solar storm known as the Carrington Event famously triggered sparks in telegraph wires on Earth. A similar event today triggering currents in our power grids could do billions of dollars in damage, so understanding how a geomagnetic storm triggers currents on Earth is really important.

Scientists were able to monitor this event using a group of NASA satellites called THEMIS, The Time History of Events and Macroscale Interactions During Substorms mission (don’t blame me I didn’t write the acronym). They found a few interesting details, all of which are hard to follow but sound really cool!

When the event started, it triggered something called a Geomagnetic Substorm. Studying these events is one of the main targets of the Themis mission. During this part of the event, the Earth’s Magnetotail, the magnetic field tail behind the planet, got tangled up and suddenly reconnected, basically releasing what the scientists described as an “explosion” of magnetic energy. That energy whipped back into the atmosphere and triggered the Aurora outbreak, which started at lower latitudes and built as it moved towards the poles.

The intersection of all this energy with the atmosphere caused the formation of a narrow, west-traveling jet of energy in the ionosphere, the layer of ionized gas in the Earth’s upper atmosphere. That rapidly moving jet of energy is called an Electrojet.

In this case, that electrojet traveled over Alaska, and the moving charges in this electrojet triggered the development of magnetic fields at the planet’s surface. Those magnetic fields were the specific trigger of electrical currents that were measureable in systems in that state.

Although the entire magnetic field system is as complicated as it sounds above, seeing pieces like this will help scientists better predict in the future what types of events are likely to trigger currents along the ground, and eventually we may even be able to issue improved warnings to shut down and protect electronic devices and systems before a really big event hits.

Yesterday, NASA is launched a spacecraft, the Parker Solar Probe, built to head only 4.5 solar diameters from the outer layer of the sun. It will analyze the features that trigger these outbreaks, far before they interact with our magnetosphere to trigger events like this.

-JBB

Image credit: Jeff Wallace https://flic.kr/p/rGBy5c

Original paper: https://doi.org/10.1029/2018SW001911