NASA space probe solves solar wind mystery

Like a gigantic showerhead, the sun spits out energetic particles at high speed. When these high-speed particles hit Earth, they create spectacular natural phenomena, but they can also disrupt our technology.

Now, thanks to NASA’s Parker Solar Probe (PSP) spacecraft, which was sent to the Sun in August 2018, scientists have discovered how such solar winds originate in the Sun’s coronal holes.

In 2021, NASA’s spacecraft came as close to the sun as any other man-made object has come before (to within 20.9 million kilometers), practically plunging into the particles of the solar corona. During this mission, the research team led by Stuart D. Bale, Professor of Physics at the University of California, Berkeley, and James Drake from the University of Maryland-College Park, was able to gain detailed insights that are lost when the solar wind breaks the surface of the planet leaves the sun in the form of a steady burst of charged particles.

“The winds carry a lot of information from the Sun to Earth, so understanding the mechanism behind the solar wind is of practical importance for Earth,” Drake said in a statement. “This will impact our ability to understand how the sun releases energy and causes geomagnetic storms that pose a threat to our communications networks.”

The results of the study were published in journal Nature published. There are two types of solar wind: the fast solar wind, which emanates from holes in the corona at the sun’s poles at a peak speed of 800 kilometers per second, and the slow solar wind, which reaches a peak speed of around 400 kilometers per second.

The researchers compare the coronal holes to showerheads, from which a relatively even jet emerges. These holes are gigantic funnels nearly 18,000 miles in diameter that Earth could fit into more than twice.

“The larger-scale convection flow is called supergranulation. Where these supergranulation cells meet and move down, they pull the magnetic field down in a kind of funnel on their way. The magnetic field is greatly amplified there because it is simply dammed up,” explains Stuart Bale.

Thanks to the discovery of some extremely high-energy particles, the research group has determined that the fast solar wind can only be generated by a phenomenon called magnetic reconnection in these funnels.

This magnetic feedback is said to be the energy source for the fast solar wind, and is substructured by small bundles of magnetic energy associated with convection currents in the coronal holes.