Origin of ‘slow’ solar wind likely to be solved

The solar wind is a stream of electrically charged particles blown out into space by the Sun. Fast solar winds (at speeds of more than 500 kilometers per second) arise from “open” regions in the Sun’s thin atmosphere (corona), where magnetic field lines “disappear” into space, allowing charged particles to escape easily. However, the origin of the slow solar wind (slower than 500 kilometers per second) has always been unclear.

The Solar Orbiter regularly flies close to the Sun at a relatively short distance, which allows for this On site– Solar wind measurements from space probes can be better compared with observations of the solar surface. In this way, a team led by Steve Yardley from Northumbria University (UK) determined that slow solar winds originate from the boundary regions of the “open” and “closed” parts of the corona.

In the “closed” region, magnetic field lines bend toward the Sun’s surface, and it is usually difficult for atomic nuclei and electrons to escape. But where “open” and “closed” areas meet, field lines can sometimes break, only to close again shortly afterwards. Solar Orbiter observations suggest that this is where to look for the origin of the slow solar wind.