ESA Space Science | Cluster | 2014 Dec 18
Auroras are the most visible manifestation of the Sun’s effect on Earth, but many aspects of these spectacular displays are still poorly understood. Thanks to ESA’s Cluster and NASA’s Image satellites working together, a particular type of very high-latitude aurora has now been explained.
Although separated by some 150 million kilometres, the Sun and Earth are connected by the solar wind. This stream of plasma – electrically charged atomic particles – is launched by the Sun and travels across the Solar System, carrying its own magnetic field with it.
Depending on how this ‘interplanetary magnetic field’ is aligned with Earth’s magnetic field when it arrives, there can be various results.
At the point where the two fields meet, Earth’s magnetic field points north. If the interplanetary field is pointing south, then ‘magnetic reconnection’ can occur, where magnetic field lines pointing in opposite directions spontaneously break and reconnect with other nearby field lines.
This opens the door to solar wind plasma entering the magnetosphere – Earth’s magnetic ‘bubble’. ...
Direct observation of closed magnetic flux trapped in the high-latitude magnetosphere - R. C. Fear et al
- Science 346(6216) 1506 (19 Dec 2014) DOI: 10.1126/science.1257377