Understanding how and where the solar wind originates helps predict solar storms that create beautiful auroras on Earth, but can also damage satellites and power grids.

NASA’s historic Parker Solar Probe mission is revolutionizing our understanding of the Sun and expanding our knowledge of the origin and evolution of the solar wind that affects Earth. The Parker probe moves through the Sun’s atmosphere, closer to the surface than any spacecraft before it, and encounters extreme heat and radiation conditions. To provide humanity with the closest observations of this star.

Closest point to the sun

Measurements from the probe, which was launched about 8.5 million kilometers from the Sun in November 2021, give us an even closer look at how the solar wind is rapidly forming as the data indicate a specific type of magnetic reconnection. According to a team of physicists led by Stuart Bell of the University of California, Berkeley and James Drake of the University of Maryland, this force of nature is driving.

In a press release published by the York Alert website, the research team said (EurekAlert) on June 7, the probe detected streams of high-energy particles similar to supergrain flows within coronal cavities (temporary regions of relatively cool, less dense plasma in the solar corona), indicating that these are regions where the wind is forming. Fast “Solar.

The team explains that coronal holes are regions where magnetic field lines emerge from the surface rather than turning inward, causing open field lines to extend outward and fill most of the space around the Sun.

Coronal cavities

These gaps are usually positioned at the poles during quiet periods on the Sun, so the fast solar wind that creates them doesn’t hit Earth, but when the Sun reverses its magnetic field every 11 years, these gaps appear across the board. At the surface, it leads to the generation of jets of solar wind that directly drive the Earth and create the beautiful aurora borealis, but can also damage satellites and the power grid.

“Winds carry a lot of information from the Sun to Earth, so understanding the mechanism behind the Sun’s wind is important for practical reasons on Earth,” says Drake. “This will affect our ability to understand how the Sun emits energy and drives geomagnetic storms. , which poses a threat to our communications networks.”

Blisters of granules

When Parker approached the Sun in November 2021, one of these coronal holes was positioned so coincidentally that the probe could collect the closest observations of these regions. The team says the data show that the coronal hole resembles the head of a “shower” where roughly evenly spaced jets emerge from “congestion” (like funneling) locations of magnetic field lines. In and out of the surface of the Sun.

“The plutosphere is covered with convective cells, it’s in a pan of boiling water, and the convective flow is broadly called supergranules, and when these supergrain cells meet and go down, they pull the magnetic field into it. This kind of path goes down through the cone.” “And the magnetic field becomes more intense there because of the jamming. It’s like a bunch of magnetic fields flowing through a drain, and what happens is the spatial separation between those little drains (or those cones). We’re seeing that now in solar probe data.”

Prefer one of the two hypotheses

Based on the presence of some high-energy particles detected by the Parker probe, particles traveling 10 to 100 times faster than the average solar wind, the researchers concluded that the wind could only form through this process called magnetic reconnection between open and closed. Magnetic fields. In a process called exchange reconnection.

Results The researchers’ findings, based on data from Parker’s study published in the journal “Nature”, suggest that the origin of the solar wind is more likely to be the hypothesis of magnetic interaction than the hypothesis of particle acceleration by electromagnetic waves in the corona. Holes, called Alfvén waves, result from interactions between heat fluxes and magnetic fields.

“The big conclusion is that magnetic reconnection within these upwelling systems is what provides the energy source for the fast solar wind,” Bell says. “It doesn’t come from everywhere in a coronal hole, it’s built up underneath these coronal holes. The supergranule cells. It comes from these little bundles.” Magnetic energy associated with convective flux. We think our results are strong evidence that reconnection does this.”