A geomagnetic storm is a phenomenon during which there is a temporary change in the magnetic field around the Earth. It is a space weather phenomenon, and its cause is linked to the Sun. But what do solar flares have to do with all this, and what happens when a geomagnetic storm erupts?
Society is strongly attached to electronic devices. Telecommunication tools or global navigation satellite systems help our daily lives, yet we sometimes forget how fragile our existing world is. A geomagnetic storm, for example, can disrupt magnetic field for days, affecting the functioning of the pieces of equipment listed as examples above.
Today, it's natural to quickly check what the weather will be like in the coming days and weeks. The need to track and forecast space weather first developed in the 20th century, perhaps not coincidentally at a time when a range of electronic devices was expanding significantly. The idea of monitoring was born in the 1950s, but it was only in the 1990s that it first received much attention. Detailed information on current space weather is available on NOAA, spaceweather.com, NASA and ESA too.
What is a geomagnetic storm and what causes it?
The cause of a geomagnetic storm is the Sun, more specifically the Sun's coronal motion (at sunspot maximum) or the high-speed flow, or solar wind (at sunspot minimum). The Sun's surface is not perfect, and from time-to-time sunspots appear on it, in which the magnetic field strength is highly concentrated. Solar flares are produced during coronal mass ejection (CME). This means that the magnetic force causes the ejected plasma cloud to move away from the Sun's surface at an accelerating rate and then transform into an interplanetary magnetic cloud. When these flares reach the Earth, we talk about a geomagnetic storm. In other words, during solar wind, the magnetic field of the Earth is depressed on the side where the solar wind hits, the magnetosphere of our planet gets more energy, the plasma flow increases, and the electric current increases in both the magnetosphere and the ionosphere. This in turn pushes the boundary between the magnetosphere and the solar wind outwards.
Throughout history, there have been many observed geomagnetic storms, the most famous being the so-called Carrington event. In late August-early September 1859, the number of sunspots increased. At this time, a strengthening of the magnetic field was recorded, and the aurora was seen in unusual areas, even around the equator. Richard C. Carrington was the first to recognise that this was due to the transient phenomena of the sun, which also affect the Earth.
A geomagnetic storm can develop in just a few hours, but its effects can be felt days later. During the Carrington event, for example, telegraphs were down for days, and compasses were disrupted. Such a phenomenon would have far more brutal consequences in modern times, paralysing modern life.
What are the danger levels?
Geomagnetic storms can be classified into 5 categories based on their strength according to the NOAA Space Weather Scale. Let's have a look at the characteristics of each category!
Mild
Mild geomagnetic storms can occur up to 1700 times in a solar cycle. Their impact is relatively small, with only network fluctuations and minor satellite malfunctions. They make it more difficult for migrating birds to find their way around, and the aurora shows itself at a higher latitude.
Moderate
Moderate magnetic storms can occur up to 600 times in a solar cycle. Power systems at higher latitudes are be alarmed, shortwave radio waves can be disrupted, and if the storm is prolonged, it can leave a mark on transformers. Spacecrafts and satellites may need to change orbits, and inaccuracy in measurements rises. The aurora is visible at a latitude of 55 degrees.
Strong
In a solar cycle, 200 events can be classified as strong geomagnetic storms. The effects are strong: power supplies need voltage adjustments, false alarms might occur in defence systems, satellites in low Earth orbit may lose speed and be more difficult to control, satellite signals and long-wave navigation systems may be disrupted, short-wave interference can happen, and the aurora is visible at 50 degrees latitude.
Serious
There are 100 major storms per solar cycle, causing significant voltage fluctuations, electrically charging the surface of space-based instruments and objects, making them increasingly difficult to control. Shortwave and satellite-longwave navigation is barely functioning, equipment may be damaged, and the aurora may appear at 45 degrees latitude.
Extraordinary
Fortunately, the number of extraordinary events is not very high, with only 4 per solar cycle. Such storms can cause power grid components to break down for long or short periods, transformers to fail, and spacecraft to lose data and tracking. Shortwave radio communications may be impossible for days, satellite navigation and longwave navigation may be disrupted for hours, and the aurora may be visible as low as 40 degrees latitude. Such a geomagnetic storm could paralyse normal communication systems.
What is the impact of a geomagnetic storm?
The geomagnetic storm causes malfunctions in GPS systems, mobile phones, the electricity grid, and telecommunications systems. Depending on the intensity of the storm, the disruption can last from a few hours to a few days.
The exact physiological impact is not yet known. There is research implying that solar flares may affect brain activity, which can impact deteriorate depression, schizophrenia, headaches, migraines, the tension in the neck, forehead and shoulder muscles, attention and concentration.
Geomagnetic storms are not directly dangerous to human life, yet a stronger one has the potential to turn our current world upside down. By monitoring space weather, such an event is becoming more predictable, and as science advances, we can learn more and more about this phenomenon.
