Geomagnetic storms are temporary disturbances in the Earth’s magnetosphere caused by changes in typical space weather. Geomagnetic storms are actually caused by the sun when a solar wind shock wave hits the Earth’s magnetic field. This occurs because the Interplanetary Magnetic Field (IMF) - the sun and earth - is disturbed. The IMF turns southward and ends up staying that way for a long period of time, causing disturbances.

Severe geomagnetic storms can last up to two and a half days. There are two phases. During the first phase, the charged particles in Earth’s near-plasma sheet become energized, getting injected into the inner magnetosphere. This causes another phase, which is called the storm-time ring current. This storm-time ring current is always present around the Earth, but geomagnetic storms cause it to fluctuate very wildly. The period of fluctuation usually lasts anywhere from 3 to 12 hours and is considered the “main phase” of the geomagnetic storm. Afterwards, the ring current returns to its normal phase. After the largest storm ever recorded in February 1986, it took over a month to return to normal.

Geomagnetic storms can have interesting effects on Earth and its inhabitants. If someone is close enough, they can cause radiation poisoning severe enough to cause cancer, chromosomal damage, and other problems. They can even cause an increase in radiation levels aboard airplanes flying at high altitudes.

There is also compelling evidence to suggest that they have an effect on biology as well. For instance, physically stressed biological systems seem to react to fluctuations in the geomagnetic field. They even affect animals that have internal biological compasses such as dolphins and whales by disrupting the bundle of nerves that allows that biological compass to function.

Geomagnetic storms also disrupt communications systems. Radio frequencies become disrupted and some disappear altogether. Ground-to air communication, ship-to-shore communication, navigational systems like GPS, and satellites can be affected in various ways. In some cases, they go haywire and other cases, they stop working completely.

Fortunately, there are many ways to keep track of geomagnetic storms. Magnetometers monitor the auroral zone where the storms occur and there are two different types of radar – incoherent and scatter radar – that are used to probe the same area. Signals are bounced off the ionosphere irregularities and graphed so that their motion can be tracked and monitored. Many of the tools used to track geomagnetic storms are actually spacecraft instruments. Besides the magnetometer, there are also electrical sensors, radio sounders, and particle detectors being used to track them.

Typical measurements of geomagnetic storms can be done at any time but when it comes to studying occurrences that have to do with the sun, most scientists fit their work into a solar cycle phase. A solar cycle lasts 11 years. The National Oceanic and Atmospheric Administration (NOAA) together with the National Aeronautics and Space Administration (NASA) keep track of geomagnetic storms.

• Glossary: Geomagnetic Storms
• Weather Scale for Geomagnetic Storms
• Introduction to Geomagnetic Storms
• The First Recorded Geomagnetic Storm
• Image Explores: Geomagnetic Storms
• Severe Geomagnetic Storm Intervals in History
• Geoeffective Conditions: What Causes Geomagnetic Storms
• Solar Activity and Geomagnetic Storms: The First 40 Years
• Geomagnetic Storm Facts
• Geomagnetic Effects on Mental Health
• Tracking A Perfect Storm
• Geometric Storms