Solar Wind - across the void to planet Earth

The sun's solar winds can have a devastating effect on the Earth particularly during periods of peak activity which are, on average around every 11 years. The solar winds or geomagnectic storms can overload power grids, disrupt communications on Earth, knock out satellites (there are around 994 in orbit around the planet at present) potentially disrupt aircraft transport using the northern polar region route as well as present a hazard to astronauts in orbit at the International Space Station. The Earth is being constantly bombarded with a stream of accelerated particles not only from the Sun, but also from interstellar and other galactic sources.

To keep an eye on the sun the Advanced Composition Explorer (ACE) managed by NASA and launched in 1997 orbits the L1 libration point which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth and 148.5 million km from the Sun. 

From this location at L1, ACE has a prime view of the solar wind, interplanetary magnetic field and higher energy particles accelerated by the Sun, as well as particles accelerated in the heliosphere and the galactic regions beyond. ACE also provides near-real-time 24 hour continuous coverage of solar wind parameters and solar energetic particle intensities (space weather). When reporting space weather ACE provides an advance warning (about one hour) of geomagnetic storms. Although the spacecraft has enough propellant on board to maintain an orbit at L1 until around 2024 it is increasingly ageing being now 14 years old.  With science funding at record lows in the US and elsewhere this is surely one mission that should be protected.

Diagram courtesy NASA