What is a Geomagnetic Storm? Causes, Effects, and History
A geomagnetic storm is a major disturbance caused by a very efficient exchange of energy from the solar wind to the space environment surrounding Earth. When the solar system ejects billions of tons of solar storms with its embedded magnetic field toward Earth, more giant storms occur.
These storms cause phenomena like power outages and satellite disruptions and create northern lights in places that wouldn’t have been possible otherwise. This article explores the hows of geomagnetic storms and the NOAA space weather scales. We will also discuss its impact and past incidents on Earth.
Table of Contents:
What is a geomagnetic storm?
A geomagnetic storm is an enormous disturbance in Earth’s magnetosphere caused by an efficient energy exchange from the solar wind into the space environment surrounding Earth. Geomagnetic storms happen because of distinct changes in the solar wind's speed, density, and magnetic properties. It is also called a solar storm.
These geomagnetic storms last for several hours or days. The sun releases an intense surge of the solar wind, also known as coronal mass ejections, that disrupts Earth’s magnetic field. The disruption caused by solar coronal mass ejections produces electric currents, which produce more variations around the earth’s magnetic field and lead to a magnetic storm.
Energetic particles enter Earth’s magnetic field, produce currents, and cause a time-dependent variation in the magnetic field. Also, the Earth produces magnetic disturbances when the sun releases a coronal mass ejection. At the same time, the Earth’s magnetosphere aligns with the sun’s.
Geomagnetic storms create strong currents in the magnetic field, changes in the system’s radiation belts, and heat the ionosphere and the upper region called the thermosphere. Near the space environment surrounding Earth, the Earth produces magnetic disturbances on the ground in a ring of westward currents. We use these currents to characterize the size of a geomagnetic storm now.
Other currents produced in space, called field-aligned currents, follow the magnetic fields and connect to other intense currents in the auroral ionosphere. Auroral currents also produce large magnetic disturbances.
Space weather caused by geomagnetic storms includes solar energetic particles (SEP), geomagnetically induced currents, ionospheric storms, and radar scintillation. Magnetic storms also cause space weather like the northern lights and aurora borealis in low-earth orbit areas. During a geomagnetic storm, your magnetic compass is more likely to be faulty.
How is it measured?
A measuring scale is used to determine the intensity of a geomagnetic storm and to know if it is strong enough to disrupt systems. Scientists monitor an increase in geomagnetic storm levels by watching the geomagnetic disturbance index, known as Kp. The index is the starting point NOAA uses to identify the most intense storms that can disrupt Earth’s systems.
NOAA’s space weather scale ratings for geomagnetic storms are:
- G-5 Extreme
G-5 storms have an index of Kp=9, occurring four days every eleven years. They affect spacecraft operations and power systems. Spacecraft nighty face challenges like charging and tracking problems, while power grids experience total blackouts because of damaged transformers.
- G-4 Severe
G-4 storms have an index of Kp=8 and occur every 60 days over an 11-year cycle. During a G-4 storm, satellite navigation is inoperable for hours, and low-frequency radio navigation is disrupted. Space crafts also experience problems with orientation, tracking satellites, and surface charging. Also, an aurora was visible in Alabama and northern California during the storm.
- G-3 Strong
G-3 storms are not as intense as G-4 and G-5, but they cause some Earth disruptions. They happen 130 days every 11 years. These days, some protection devices trigger the power systems’ false alarms. They also affect spacecraft operations through drag that may increase on low-earth-orbit satellites and some orientation problems.
Aurora borealis is visible in Illinois and Oregon because they are 50 degrees in the geomagnetic latitude. Also, low-frequency radio navigation and intermittent satellite navigation may happen.
- G-2 Moderate
With an index of Kp=6, moderate geomagnetic storms happen 360 days every 11 years. It may cause high-latitude power systems to experience voltage alarms, and long-duration storms may cause transformer damage. High-frequency radio propagation fades at high latitudes, and aurora borealis is visible in New York and Idaho.
- G-1 Minor
Minor storms occur 900 days every 11 years and don’t have the intense effect of other storm ratings. They might cause weak power grid fluctuations and weakly affect satellite operations. They also affect migratory animals; the aurora is visible from higher latitudes.
Effects of Geomagnetic Storms
Geomagnetic storms can disrupt navigation systems like the Global Navigation Satellite System (GNSS). Solar storms can also produce harmful geomagnetic-induced currents (GICs) in the power grid and pipelines. Do not worry; solar wind and flares do not affect human health.
Geomagnetic-induced currents are a threat to high-voltage transformers, the backbone of the power grid. Transformers can't handle direct currents, leading to overheating in the transformers’ core and windings. Overheating leads to more significant problems like damaged insulation and magnetic properties, and eventually, the transformer stops working.
Solar flares rarely have a direct impact on Earth’s surface. The solar maximum range is in a near-earth space environment, and Earth’s magnetosphere prevents solar flares from reaching Earth. However, a solar flare and intense currents of solar wind emit X-rays that disrupt radio communications.
Solar activity in the ionosphere can disrupt radio waves. Earth can lose radio signals for a few minutes to several hours. Records show an average of 2000 radio blackouts during each solar cycle.
Another effect of geomagnetic storms is solar radiation storms. Solar radiation storms occur when solar flares and coronal mass ejections simultaneously produce large protons and other particles. These protons and particles increase the radiation levels near Earth to dangerous levels.
History of Geomagnetic Storms
We discovered everything about geomagnetic storms and solar wind 210 years ago. Several storms have occurred since the 1800s. Here are some examples of storms that have happened on Earth:
Carrington event of 1859
The storm occurred between August 28 and September 2, 1859, and is one of the most significant space weather events ever recorded. Two coronal mass ejections caused it. The second flare was so intense that it triggered a geomagnetic storm that destroyed 5% of Earth’s ozone layer.
Scientists classify the storm as an X-class flare because X-class flares are intense storms. It disrupted 200,000 km of telegraph lines, rendering them useless for over 8 hours. The aurora was red and lasted for several hours. They named the geomagnetic event Carrington after one of the astronomers who documented it4.
New York Railroad Superstorm of 1921
The storm in New York in May 1921 was one of the most significant storms in history. Coronal mass ejections produced large magnetic disturbances, disturbing telephone and telegraph lines. The storm temporarily put the New York Central Railroad out of service3.
May 1967 Cold War Solar Flare
This storm happened at the peak of the Cold War. It nearly changed America's history because the US government almost ordered an airstrike on the Soviets when the radio communication lines went down. They thought the Soviets had jammed the communication systems. Luckily, the Air Force’s space weather forecasters monitored the space weather and alerted them in time1.
March 1989 Geomagnetic Storm
The sun released a powerful coral mass ejection on March 10, 1989; by March 13, a geomagnetic storm hit Earth. The storm was so intense that we could see the northern lights from Texas and Florida. It created intense underground currents around most of North America. Also, 6 million residents lost power to their homes in Canada2 because of a nine-hour blackout caused by the storm.
October 2003 Halloween Solar Storms
The Halloween 2003 event produced flares so intense it overloaded the measuring sensors. It was one of the most potent space weather events after the Carrington. Scientists estimate that humanity will have to wait another century to witness a solar flare producing significant magnetic disturbances of this magnitude5.
Conclusion
While the storms create beautiful auroras, they may also disrupt navigation systems and create hazardous GCIs in electricity lines or pipelines. An increased geomagnetic disturbance index of Kp arose. Luckily, the storms do not harm humans and can’t destroy the earth.
Glossary Terms:
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| 2 | Liu, Y. D., Luhmann, J. G., Kajdič, P., Kilpua, E. K., Lugaz, N., Nitta, N. V., Möstl, C., Lavraud, B., Bale, S. D., Farrugia, C. J., & Galvin, A. B. (2014). Observations of an extreme storm in interplanetary space caused by successive coronal mass ejections. Nature Communications, 5(1). |
| 3 | Love, J. J., Hayakawa, H., & Cliver, E. W. (2019). Intensity and impact of the New York Railroad superstorm of May 1921. Space Weather, 17(8), 1281–1292. |
| 4 | Green, J. L., & Boardsen, S. (2006). Duration and extent of the great auroral storm of 1859. Advances in Space Research, 38(2), 130–135. |
| 5 | Curto, J. J., Castell, J., & Del Moral, F. (2016). Sfe: waiting for the big one. Journal of Space Weather and Space Climate, 6, A23. |
Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.
Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.
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