Why a Geomagnetic Storm Makes for Pretty Skies and Tech Scares

The combination of solar activity and our planet's magnetic field can make for some pretty interesting results. GeorgePeters / Getty Images

When the Sun gets rowdy, Earth feels it. A geomagnetic storm happens when solar activity stirs up Earth’s magnetic field, producing large magnetic disturbances that can mess with everything from navigation systems to power grids.

These storms are a big deal in space weather, which is why scientists issue geomagnetic storm watches to keep tabs on the space environment surrounding Earth.

You can thank the Sun for the trouble. During periods of high solar activity, the Sun ejects massive bursts of charged particles and magnetic fields, known as solar coronal mass ejections (CMEs). These CMEs hurl billions of tons of solar material into space, and if one barrels toward Earth, it can slam into Earth's magnetosphere. That’s when the action really starts.

How Solar Wind Sparks a Magnetic Meltdown

The solar wind — a continuous stream of charged particles flowing from the Sun — carries with it the Sun's magnetic field.

When this wind hits Earth's magnetic field, especially during a CME or from a coronal hole emitting high speed solar wind, it causes a very efficient exchange of energy.

This process, called magnetic reconnection, sends energetic particles zipping into Earth's upper atmosphere and ionosphere. These particles collide with atoms, add energy to the ionosphere and create stunning light shows like the aurora borealis.

aurora borealis — You can catch the Northern Lights in far-north places like Alaska.
Noppawat Tom Charoensinphon / Getty Images

But they also generate auroral currents and field aligned currents that create strong horizontal variations in Earth’s magnetic field. These magnetic deviations can disrupt systems on the ground and in orbit.

Why Magnetic Disturbances Disrupt Earthly Systems

The Earth produces magnetic disturbances naturally, but intense storms from space can cause sudden and severe magnetic field changes.

When geomagnetic storms peak — during a period known as the main phase — they create intense currents, especially a westward current in the magnetosphere. This disturbance storm time (Dst) index tells us how severe a magnetic storm is.

All this activity induces electric currents in the ground. Known as harmful geomagnetic induced currents (GICs), these can overload and damage power grid transformers. That’s a serious problem for electricity providers.

electric disruption — Well that's not a good sign.
Erlon Silva - TRI Digital / Getty Images

GICs can also affect pipelines and railways, whereas storm-driven disturbances in Earth’s ionosphere disrupt radio signals and navigation systems that rely on the global navigation satellite system (GNSS).

How Space Weather Affects Satellites and Communication

The space environment becomes hostile during a geomagnetic storm.

Charged particles and energetic radiation from solar storms can damage satellites in low Earth orbit and those further out. These storms increase ionospheric density and local heating in the upper atmosphere region called the auroral ionosphere, which can drag satellites out of orbit.

Communication systems aren’t safe either. Radio signals can be absorbed or scattered, particularly those used in aviation and maritime operations. Satellite-based navigation systems like GNSS can create errors or even fail, especially when space weather conditions are extreme.

Predicting and Preparing for Geomagnetic Storms

The National Oceanic and Atmospheric Administration (NOAA) keeps a close eye on the Sun through its Space Weather Prediction Center. They use the NOAA space weather scales to rate the severity of geomagnetic activity and issue alerts when solar storms are brewing.

Understanding the solar cycle helps scientists predict periods of increased solar activity. During solar maximum, when the Sun’s magnetic field flips and sunspots peak, more CMEs and solar flares occur. CMEs send shock waves and embedded magnetic fields hurtling through the solar system.

When a fast CME is directed toward Earth and strikes our planet’s magnetosphere, it can compress Earth’s dayside magnetic field and trigger a major geomagnetic storm.

Preventive measures are crucial. Engineers design power grid systems to handle magnetic storms, and satellite operators adjust orbits or shut down sensitive equipment. By studying how magnetic storms develop and behave, we can better protect the technology that keeps our world humming.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.