The wind blows on Earth. It is the result of movements of air masses in our atmosphere. But another type of wind also blows on our planet. The solar wind, made up of charged particles emitted by the Sun. The Solar Orbiter mission has successfully traced back to the sources of this wind.
The wind is an air current. It forms when air expands due to heat, rises into the Earth’s atmosphere, and exerts pressure on the surrounding air. However, what scientists call the solar wind corresponds to a different phenomenon. It is a kind of flow of electrically charged particles emitted by the Sun. This flow, as astronomers know, is as variable as our wind. Its speed, density, or composition – mainly in electrons and protons – can change over time and depending on the region of the Sun it comes from.
What astronomers know less about is where this solar wind actually comes from. More precisely, where the so-called slow solar wind comes from. Researchers distinguish between two types of solar wind. The fast solar wind consists of particles moving at over 500 km/s. It emanates from coronal holes, regions where magnetic field lines are only connected to the Sun at one end. The slow solar wind, on the other hand, does not exceed 500 km/s. Astronomers suppose that it is linked to the active regions of our star. These are the regions where solar flares are born, where magnetic fields twist and concentrate, and sometimes break and reconnect. However, the details of the process are still not fully understood by science.
The Importance of Understanding the Mechanism Behind the Solar Wind
Yet, understanding where the solar wind originates is crucial. Because in its journey through our star, it affects not only the planets but also the spacecraft and technological infrastructure in space. By unraveling the mysteries of the solar wind, scientists can better predict space weather events and protect our technology from its impacts.
The Solar System, it interacts with celestial bodies – like Earth – and spacecraft. Solar wind is responsible for both the beautiful auroras that can light up our sky and the damage that can occur to our electrical systems, probes, or satellites.
One of the greatest mysteries of the Sun has finally been revealed by the Solar Orbiter probe. The Solar Orbiter mission, launched in 2020, has the exact goal of confirming the origin of solar wind. In the journal Nature Astronomy, researchers report that data collected during its very first close pass to the Sun in early March 2022 have delivered their verdict. The Solar Orbiter mission was only about 75 million kilometers away from the star (half the distance between Earth and the Sun).
Solar Orbiter, with the right instruments to track solar wind, can measure both solar wind and the magnetic field directly around it, as well as remotely capture images of our Sun and other data. By combining these two sets of data, astronomers can position the mission to capture solar wind from specific regions of the Sun, such as a coronal hole and an active region.
Researchers have observed how solar wind changes speed – from fast to slow or vice versa – as well as composition, temperature, and density when recorded above one region or the other. This confirms that, as expected, coronal holes expel particle streams that travel into space at speeds of over 1.8 million kilometers per hour. And that solar spot clusters do emit a slower type of solar wind. It’s as if the solar wind carries “imprints” from its different source regions.