Artist’s concept of the Parker Solar Probe spacecraft approaching the sun. Launched in 2018, the probe is increasing our ability to forecast major space-weather events that impact life on Earth. Credit: NASA
NASA’s Parker Solar Probe (PSP) has flown close enough to the sun to detect the fine structure of the solar wind close to where it is generated at the sun’s surface, revealing details that are lost as the wind exits the corona as a uniform blast of charged particles.
It’s like seeing jets of water emanating from a showerhead through the blast of water hitting you in the face.
In a paper to be published in the journal Nature, a team of scientists led by Stuart D. Bale, a professor of physics at the University of California, Berkeley, and James Drake of the University of Maryland-College Park, report that PSP has detected streams of high-energy particles that match the supergranulation flows within coronal holes, which suggests that these are the regions where the so-called “fast” solar wind originates.
Coronal holes are areas where magnetic field lines emerge from the surface without looping back inward, thus forming open field lines that expand outward and fill most of space around the sun. These holes are usually at the poles during the sun’s quiet periods, so the fast solar wind they generate doesn’t hit Earth. But when the sun becomes active every 11 years as its magnetic field flips, these holes appear all over the surface, generating bursts of solar wind aimed directly at Earth.
Understanding how and where the solar wind originates will help predict solar storms that, while producing beautiful auroras on Earth, can also wreak havoc with satellites and the electrical grid.
“Winds carry lots of information from the sun to Earth, so understanding the mechanism behind the sun’s wind is important for practical reasons on Earth,” Drake said. “That’s going to affect our ability to understand how the sun releases energy and drives geomagnetic storms, which are a threat to our communication networks.”
Based on the team’s analysis, the coronal holes are like showerheads, with roughly evenly spaced jets emerging from bright spots where magnetic field lines funnel into and out of the surface of the sun. The scientists argue that when oppositely directed magnetic fields pass one another in these funnels, which can be 18,000 miles across, the fields often break and reconnect, slinging charged particles out of the sun.
“The photosphere is covered by convection cells, like in a boiling pot of water, and the larger scale convection flow is called supergranulation,” Bale said. “Where these supergranulation cells meet and go downward, they drag the magnetic field in their path into this downward kind of funnel. The magnetic field becomes very intensified there because it’s just jammed. It’s kind of a scoop of magnetic field going down into a drain. And the spatial separation of those little drains, those funnels, is what we’re seeing now with solar probe data.”
Based on the presence of some extremely high-energy particles that PSP has detected—particles traveling 10 to 100 times faster than the solar wind average—the researchers conclude that the wind could only be made by this process, which is called magnetic reconnection. The PSP was launched in 2018 primarily to resolve two conflicting explanations for the origin of the high-energy particles that comprise the solar wind: magnetic reconnection or acceleration by plasma or Alfvén waves.
“The big conclusion is that it’s magnetic reconnection within these funnel structures that’s providing the energy source of the fast solar wind,” Bale said. “It doesn’t just come from everywhere in a coronal hole, it’s substructured within coronal holes to these supergranulation cells. It comes from these little bundles of magnetic energy that are associated with the convection flows. Our results, we think, are strong evidence that it’s reconnection that’s doing that.”
The funnel structures likely correspond to the bright jetlets that can be seen from Earth within coronal holes, as reported recently by Nour Raouafi, a co-author of the study and the Parker Solar Probe project scientist at the Applied Physics Laboratory at Johns Hopkins University. APL designed, built, manages and operates the spacecraft.
Plunging into the sun
By the time the solar wind reaches Earth, 93 million miles from the sun, it has evolved into a homogeneous, turbulent flow of roiling magnetic fields intertwined with charged particles that interact with Earth’s own magnetic field and dump electrical energy into the upper atmosphere. This excites atoms, producing colorful auroras at the poles, but has effects that trickle down into Earth’s atmosphere. Predicting the most intense winds, called solar storms, and their near-Earth consequences is one mission of NASA’s Living With a Star program.
The probe was designed to determine what this turbulent wind looks like where it’s generated near the sun’s surface, or photosphere, and how the wind’s charged particles—protons, electrons and heavier ions, primarily helium nuclei—are accelerated to escape the sun’s gravity.
To do this, PSP had to get closer than 25 to 30 solar radii, that is, closer than about 13 million miles.
“Once you get below that altitude, 25 or 30 solar radii or so, there’s a lot less evolution of the solar wind, and it’s more structured—you see more of the imprints of what was on the sun,” Bale said.
In 2021, PSP’s instruments recorded magnetic field switchbacks in the Alfvén waves that seemed to be associated with the regions where the solar wind is generated. By the time the probe reached about 12 solar radii from the surface of the sun—5.2 million miles—the data were clear that the probe was passing through jets of material, rather than mere turbulence. Bale, Drake and their colleagues traced these jets back to the supergranulation cells in the photosphere, where magnetic fields bunch up and funnel into the sun.
But were the charged particles being accelerated in these funnels by magnetic reconnection, which would slingshot particles outward, or by waves of hot plasma—ionized particles and magnetic field—streaming out of the sun, as if they’re surfing a wave?
The fact that PSP detected extremely high-energy particles in these jets—tens to hundreds of kiloelectron volts (keV), versus a few keV for most solar wind particles—told Bale that it has to be magnetic reconnection that accelerates the particles and generates the Alfvén waves, which likely give the particles an extra boost.
“Our interpretation is that these jets of reconnection outflow excite Alfvén waves as they propagate out,” Bale said. “That’s an observation that’s well known from Earth’s magnetotail, as well, where you have similar kind of processes. I don’t understand how wave damping can produce these hot particles up to hundreds of keV, whereas it comes naturally out of the reconnection process. And we see it in our simulations, too. ”
The PSP won’t be able to get any closer to the sun than about 8.8 solar radii above the surface—about 4 million miles—without frying its instruments. Bale expects to solidify the team’s conclusions with data from that altitude, though the sun is now entering solar maximum, when activity becomes much more chaotic and may obscure the processes the scientists are trying to view.
“There was some consternation at the beginning of the solar probe mission that we’re going to launch this thing right into the quietest, most dull part of the solar cycle,” Bale said. “But I think without that, we would never have understood this. It would have been just too messy. I think we’re lucky that we launched it in the solar minimum.”
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NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
