Geomagnetic storms are disturbances in Earth's magnetic field that last from a few hours to several days. They originate from external sources and result from a sudden surge of particles emitted by solar flares that reach the magnetosphere, creating changes in Earth's magnetic field. Geomagnetic storms are global in nature and begin at all points on Earth simultaneously. However, the magnitude of observed storms varies from place to place, and the higher the latitude, the greater the magnitude.
In this article we are going to tell you what geomagnetic storms are, what their characteristics and danger are.
Formation of geomagnetic storms
The occurrence of geomagnetic storms is related to solar activity. The sun is constantly emitting particles in what is called the "solar wind." These particles usually do not penetrate Earth's atmosphere because they are deflected by Earth's magnetosphere.
However, the Sun does not have a constant activity, but rather exhibits activity that varies over a duration of 11 years, in the so-called "solar cycle", which is quantified by the number of sunspots it sees in each period. moment. . During this 11-year cycle, the Sun has varied from minimal activity with nearly disappearing sunspots to maximal activity with a significant increase in sunspot number.
Sunspots correspond to cooler regions in the Sun's photosphere where the magnetic field is very strong and are considered active regions of the Sun. Solar flares and coronal mass ejections (CMEs) occur in these sunspots. A solar flare is a violent eruption that throws large amounts of coronal material into interplanetary space, thus modifying the density and speed of the solar wind. For more information on this process, you can consult the article on solar storms.
When CMEs are large enough and occur in Earth's direction, the increased density and speed of the solar wind can warp Earth's magnetosphere, creating geomagnetic storms. These affect the entire planet at the same time, and depending on how fast the solar wind reaches violently expelling, they can take a day or a few days to occur, since this phenomenon occurs on the Sun.
In recent years, a series of satellite missions have been launched into space to monitor solar activity from different locations and to provide early warnings of coronal mass ejections that could affect Earth. To learn more about this monitoring, you can read the article on space weather.
How to measure geomagnetic storms?
A geomagnetic storm is recorded at geomagnetic observatories as a fairly sudden disturbance that affects components of the Earth's magnetic field and persists for a day or more until calm is restored.
To quantify the magnitude of geomagnetic storms, the Geomagnetic Index was used. Of these, the most commonly used are the Dst index, which represents the magnetic activity of a network of four geomagnetic observatories located near the magnetic equator, and the three-hour index, which represents the activity.
Geomagnetism is performed every three hours. Among the latter, the K index is the most used, which is a quasi-logarithmic geomagnetic index, which represents the disturbance of the local geomagnetic field, and is based on the diurnal variation curve of the geomagnetic observatory on calm days. This is measured at three hour intervals. At a planetary level, the Kp index is defined, which is obtained by calculating the weighted average of the K indices observed in a global network of geomagnetic observatories.
The US agency NOAA has defined a scale to quantify the intensity and impact of geomagnetic storms. It consists of five possible values ​​(G1 to G5) related to the Kp index value reached and represents the average frequency with which they occur in each solar cycle . If you would like to learn more about this scale, please see the article on geomagnetism.
Space Weather involves the study of environmental conditions between the Sun and Earth caused by solar activity and the risks associated with it.
Currently, there are many organizations around the world that specialize in space weather, working to monitor the sun and its impact on Earth, aggregating data from satellites, geomagnetic observatories, and other sensors. In Spain, the National Space Meteorology Service (SEMNES) is carrying out these monitoring and dissemination missions, with the participation of the National Geographic Institute providing data from its geomagnetic observatory.
Effects of geomagnetic storms
The Auroras
Geomagnetic storms are usually small-scale and cause no damage. The Northern Lights in the Northern Hemisphere and the Southern Lights in the Southern Hemisphere are the most beautiful manifestations of geomagnetic storms, created by charged solar particles interacting with Earth's atmosphere. When a large amount of material arrives due to the influence of a coronal mass ejection, Earth's magnetic field attempts to deflect these particles, but they eventually penetrate the area near the magnetic poles and make contact with the upper layers of the atmosphere. In these layers, the particles interact with the atmospheric gases (oxygen, nitrogen), which then react with each other, creating the colors we see.
Although auroras are common at high latitudes, when associated with extreme geomagnetic storms, they can be seen at much lower latitudes. For example, the great Carrington Event of September 1, 1859, produced auroras in Europe, Central America, and Hawaii. In Spain, this phenomenon was very noticeable and was reported by local media at the time. To learn more about this phenomenon, we suggest reading about the Northern Lights.
Geomagnetic storm damage
In less common cases where geomagnetic storms are more intense, they can cause damage to infrastructure and people.
On the one hand, satellites are at risk of being affected by charged energetic particles, which can damage their structure or impair their operation . This could affect positioning systems, navigation systems, or communications satellites, causing significant damage and financial losses to the entire infrastructure that relies on these systems to operate.
On the other hand, power distribution networks and underground metal pipes that can induce geomagnetically induced currents (GICs) are highly sensitive. This type of current can be extremely damaging to electrical grids, causing high-voltage transformers to overheat or even burn out, as happened during the geomagnetic storm of March 13, 1989, which caused a famous blackout in Quebec , Canada. Oil and gas pipelines are susceptible to corrosion due to GICs, while railway signaling systems can be damaged, posing a risk.
People are also affected by strong geomagnetic storms when traveling by plane. For this reason, aircraft on polar routes are often diverted during intense geomagnetic storms, and astronauts must remain on board until the effects of the storm subside.
I hope that with this information you can learn more about geomagnetic storms and their characteristics.
