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

Space-monitoring agencies have predicted that a strong geomagnetic storm is likely to hit the earth.

• 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.

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.
• 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.

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.