Recently, the Sun has ejected coronal mass particles towards the Earth at a rate of 3.3 million km per hour. Can these particles affect our artificial satellites' signals, and why coronal mass ejections happen on the Sun?
According to Wikipeia on Coronal mass ejection (CME):
Recent scientific research has shown that the phenomenon of magnetic reconnection is responsible for CME and solar flares. Magnetic reconnection is the name given to the rearrangement of magnetic field lines when two oppositely directed magnetic fields are brought together. This rearrangement is accompanied with a sudden release of energy stored in the original oppositely directed fields.
Effects on artificial satellites are best explained in NASA Goddard Space Flight Center's article on Space weather and impact of solar flares on human activities:
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.
Other effects of CME include increase in the atmospheric drag of the artificial satellites, so that their orbital velocity decreases, hence might need to re-boost more frequently. Previously mentioned NASA's article goes on to explain the reason for this:
The x-rays from flares are stopped by our atmosphere well above the Earth's surface. They do disturb the Earth's ionosphere, however, which in turn disturbs some radio communications. Along with energetic ultraviolet radiation, they heat the Earth’s outer atmosphere, causing it to expand. This increases the drag on Earth-orbiting satellites, reducing their lifetime in orbit. Also, both intense radio emission from flares and these changes in the atmosphere can degrade the precision of Global Positioning System (GPS) measurements.
But satellites in LEO (Low Earth Orbit) are shielded from CMEs by the magnetosphere of the Earth, because of their proximity to it where the Earth's magnetic field is still strong, and mostly experience drag due to expansion of gases in the Earth's upper atmosphere. They are also affected by Geomagnetic storms.