Three solar phenomena – coronal holes, solar flares, and CMEs – are responsible for most of the space weather experience. Coronal holes allow the solar wind to flow away from the sun unhindered by solar magnetic fields. As we have seen, when the solar wind hits Earth, it causes the Earth’s magnetosphere to contract and expand after the solar wind passes by. These changes can cause electromagnetic interference (usually minor) on the earth.
More serious are solar flares, which bathe the Earth’s upper atmosphere with X-rays, high-energy particles, and intense ultraviolet radiation. X-rays and ultraviolet radiation can ionize atoms in the Earth’s upper atmosphere, and free electron can build up charge on the surface of a spacecraft. When this static charge is discharged it can damage the electronic components of the spacecraft, For example, you can receive shock when you walking across a carpet in dry weather, and then touching a light switch or other metal objects.
Most disturbing are coronal mass ejections. A CME is an erupting bubble of tens of millions of tons of gas that escapes from the sun into space. When this bubble reaches Earth a few days after leaving the Sun, it warms the ionosphere, which expands and moves on in space. As a result, the friction between the atmosphere and the spacecraft increases and pulls the satellites to lower altitudes.
At the time of a particularly strong flare and CME in March 1989, the system that was responsible for tracking around 19,000 objects in orbit around the earth temporarily lost sight of 11,000 of them because their orbits were changed by the expansion of the earth’s atmosphere. During the solar maximum, several satellites are brought to such a low altitude that they are destroyed by friction with the atmosphere. Both the Hubble Space Telescope and the International Space Station (ISS) require boosters at higher altitudes to stay in orbit.
