It affects it by the intense clouds of high energy particles that it often contains which are produced by solar storms. When these clouds, called coronal mass ejections, make their way to the Earth in 3-4 days, they collide with the magnetic field of the Earth and cause it to change its shape. The particles then leak through the magnetic field of the Earth, particularly near the north and south poles, and cause still more changes to the magnetic field of the Earth, this time at even lower altitudes closer to the ground. These changes can produce many problems with electrical equipment. The way on which solar wind 'plasma' invades the Earth's magnetic field and seeps into the inner regions where the van Allen radiation belts are located, is not very well known. Also, in the direction opposite the Sun, the Earth's magnetic field is pulled way out into interplanetary space making it look like a comet. In this 'geotail' region many different electrical disturbances take place that can accelerate particles to very high speeds and energies. All of this is made much more violent by the solar wind, especially the storm clouds that the Sun launches our way from time to time!
The most serious effects on human activity occur during major
geomagnetic storms. It is now understood that the major geomagnetic storms are induced by coronal mass ejections (CMEs). Coronal mass ejections are usually associated with flares, but sometimes no flare is observed when they occur. Like flares, CMEs are more frequent during the active phase of the Sun's approximately 11 year cycle. The last maximum in solar activity, the maximum of the current solar cycle, was in April, 2014.
Coronal mass ejections are more likely to have a significant effect on our activities than flares because they carry more material into a larger volume of interplanetary space, increasing the likelihood that they will interact with the Earth. While a flare alone produces high-energy particles near the Sun, some of which escape into interplanetary space, a CME drives a shock wave which can continuously produce energetic particles as it propagates through interplanetary space. When a CME reaches the Earth, its impact disturbs the Earth's
magnetosphere, setting off a geomagnetic storm. A CME typically takes 3 to 5 days to reach the Earth after it leaves the Sun. Observing the ejection of CMEs from the Sun provides an early warning of geomagnetic storms. Only recently, with SOHO, has it been possible to continuously observe the emission of CMEs from the Sun and determine if they are aimed at the Earth.
One serious problem that can occur during a geomagnetic storm is damage to Earth-orbiting satellites, especially those in high,
geosynchronous orbits. Communications satellites are generally in these high orbits. Either the satellite becomes highly charged during the storm and a component is damaged by the high current that discharges into the satellite, or a component is damaged by high-energy particles that penetrate the satellite. We are not able to predict when and where a satellite in a high orbit may be damaged during a geomagnetic storm.
Astronauts on the Space Station are not in immediate danger because of the relatively low orbit of this manned mission. They do have to be concerned about cumulative exposure during space walks. The energetic particles from a flare or CME would be dangerous to an astronaut on a mission to the Moon or Mars, however.
Another major problem that has occurred during geomagnetic storms has been the temporary loss of electrical power over a large region. The best known case of this occurred in 1989 in Quebec. High currents in the
magnetosphere induce high currents in power lines, blowing out electric transformers and power stations. This is most likely to happen at high latitudes, where the induced currents are greatest, and in regions having long power lines and where the ground is poorly conducting.