What are they?

• Solar storms/wind are magnetic plasma ejected at great speed from the solar surface. They occur during the release of magnetic energy associated with sunspots (‘dark’ regions on the Sun that are cooler than the surrounding photosphere), and can last for a few minutes or hours. 
• A geomagnetic storm is a major disturbance of Earth’s magnetosphere that occurs when there is a very efficient exchange of energy from the solar storm into the space environment surrounding Earth. 
• These storms result from variations in the solar wind that produce major changes in the currents, plasmas, and fields in Earth’s magnetosphere. 

What causes them?

• They are associated with solar coronal mass ejections (CMEs) where a billion tons or so of plasma from the sun, with its embedded magnetic field, arrives at Earth. CMEs typically take several days to arrive at Earth, but have been observed, for some of the most intense storms, to arrive in as short as 18 hours. 
• Another solar wind disturbance that creates conditions favorable to geomagnetic storms is a high-speed solar wind stream (HSS).

Conditions of formation

• The solar wind conditions that are effective for creating geomagnetic storms are-
  • sustained (for several to many hours) periods of high-speed solar wind
  • a southward directed solar wind magnetic field (opposite the direction of Earth’s field) at the dayside of the magnetosphere. This condition is effective for transferring energy from the solar wind into Earth’s magnetosphere.

How does it impact us

Not all solar flares reach Earth, but solar flares/storms, solar energetic particles (SEPs), high-speed solar winds, and coronal mass ejections (CMEs) that come close can impact space weather in near-Earth space and the upper atmosphere.

• Risk for Communication Equipment- Solar storms can hit operations of space-dependent services like global positioning systems (GPS), radio, and satellite communications. Geomagnetic storms interfere with high-frequency radio communications and GPS navigation systems.  The local heating also creates strong horizontal variations in the in the ionospheric density that can modify the path of radio signals and create errors in the positioning information provided by GPS.
• Risk for  Power grids– Geomagnetic storms can cause geomagnetic induced currents (GICs) in power grids and pipelines.
• Changes in atmosphere- Storms also result in intense currents in the magnetosphere, changes in the radiation belts, and changes in the ionosphere, including heating the ionosphere and upper atmosphere region called the thermosphere.
  • CMEs, with ejectiles loaded with matter travelling at millions of miles an hour, can potentially create disturbances in the magnetosphere, the protective shield surrounding the Earth.
• Flight Risk- Flights of aircraft and space exploration programmes are also at risk. During geomagnetic storms, passengers in airplanes are exposed to more harmful radiation, and sensitive electronics onboard are also affected.
• Risk for Satellites– During storms, the currents in the ionosphere, as well as the energetic particles that precipitate into the ionosphere add energy in the form of heat that can increase the density and distribution of density in the upper atmosphere, causing extra drag on satellites in low-earth orbit, which could lead to de-orbiting of satellites. 
• Health issues- Astronauts on spacewalks face health risks from possible exposure to solar radiation outside the Earth’s protective atmosphere.

Positive impact

• Storms can cause the appearance of beautiful auroras, also known as the northern and southern lights.

How can they be predicted

• Solar physicists and other scientists use computer models to predict solar storms and solar activities in general. 
• Current models can predict the arrival time and speed of a storm. However, the structure or orientation of the storm cannot be predicted. Certain magnetic field orientations can cause the magnetosphere to respond more intensely, resulting in more intense magnetic storms.

Why in News:

• Spacex Starlink’s newest fleet of satellites dragged out of orbit(de-orbiting) after being struck by a geomagnetic storm.

References:

1. https://www.swpc.noaa.gov/phenomena/geomagnetic-storms
2. https://indianexpress.com/article/explained/geomagnetic-storm-that-killed-starlink-sats-7764995/
3. https://www.thehindu.com/sci-tech/science/spacex-satellites-falling-out-of-orbit-after-solar-storm/article38403487.ece