A geomagnetic storm is expected to hit the earth. What is it, and how is it caused?

Geomagnetic storms can cause power outages and impact long-range radio communication and GPS devices.

Geomagnetic storms can cause power outages and impact long-range radio communication and GPS devices.

The story so far: Space-monitoring agencies have predicted that a strong geomagnetic storm is likely to hit the earth on April 14-15, 2022. The Centre for Excellence in Space Sciences, India said that there is a “very high probability of earth impact” due to solar activity causing the phenomenon.

The Space Weather Prediction Centre (SPWC) under the National Oceanic and Atmospheric Administration (NOAA) of the U.S. government has issued two geomagnetic storm watches — one each for April 14 and April 15. The storm on April 14 is expected to be moderate in strength while the one on April 15 is predicted to be minor.

What is a geomagnetic storm?

A geomagnetic storm is a disturbance in the earth’s magnetosphere, which is the area around the planet controlled by its magnetic field. The earth’s magnetosphere protects its inhabitants from most of the particles emitted by the sun. When a coronal mass ejection (CME) or a high-speed stream reaches the earth, it strikes the planet’s magnetosphere. If the incoming solar magnetic field is directed southwards, it interacts strongly with the earth’s own magnetic field that is opposite in direction, causing disturbances. The changes produced in the earth’s magnetic field as a result of this interaction allow solar wind particles to stream down the magnetic field lines and hit the atmosphere near the poles.

Solar winds deeply impact the shape of the earth’s magnetosphere, and variations in solar winds cause geomagnetic storms on earth.

At the surface of the earth, a geomagnetic storm can result in a rapid decline in the earth’s magnetic field strength. This decrease can last for around 6 to 12 hours and gradually recovers over several days.

The geomagnetic storm in question was predicted after dead sunspot AR2987 exploded, expelling a CME towards the earth. The incoming CME is predicted to cause a storm categorised as G-2, or moderate.

Sunspots are dark areas on the solar surface and contain strong, shifting magnetic fields. These are formed when areas on the surface of the sun cool slightly – from around 6,000 °C to about 4,200 °C — due to strong magnetic fields that emerge through the solar surface. Sunspots appear as dark spots against the otherwise bright sun.

What is a coronal mass ejection (CME)?

A coronal mass ejection is a large expulsion of plasma and magnetic field from the sun’s corona. Plasma is the highly ionised gas present on the sun, while corona is the outermost part of the sun’s atmosphere.

The corona is structured by strong magnetic fields. If these fields are closed, the solar atmosphere can release sudden, violent bubbles of gas and magnetic fields which constitute the CME. One large CME is capable of containing a billion tonnes of matter. CMEs can travel at varying speeds – as slow as 250 km per second to as high as 3,000 km per second.

What are the hazards associated with geomagnetic storms?

According to the U.S. Geological Survey (USGS), geomagnetic storms can impact long-range radio communication and global positioning system (GPS) devices. These storms can also damage satellite electronics and expose astronauts and high-altitude pilots to increased levels of radiation.

Voltage surges due to altered magnetic activity can also affect power supply on the earth and cause outages.

Geomagnetic storms are also linked with intensified northern lights visible in the skies of higher latitudes.


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