The fastest winds ever recorded on Earth reached more than 200 miles per hour, but even those gusts pale in comparison to the sun’s wind.

In a paper published June 7, 2023 in the journal Nature, a team of researchers used data from NASA’s Parker Solar Probe to explain how the solar wind is capable of surpassing speeds of 1 million miles per hour. They discovered that the energy released from the magnetic field near the sun’s surface is powerful enough to drive the fast solar wind, which is made up of ionized particles—called plasma—that flow outward from the sun.

This illustration shows NASA’s Parker Solar Probe near the sun. Credit: NASA/Johns Hopkins APL/Steve Gribben. This illustration shows NASA’s Parker Solar Probe near the sun. Credit: NASA/Johns Hopkins APL/Steve Gribben.

James Drake, a Distinguished University Professor in the University of Maryland’s Department of Physics and Institute for Physical Science and Technology (IPST), co-led this research alongside first author Stuart Bale of UC Berkeley. Drake said scientists have been trying to understand solar wind drivers since the 1950s—and with the world more interconnected than ever, the implications for Earth are significant.

The solar wind forms a giant magnetic bubble, known as the heliosphere, that protects planets in our solar system from a barrage of high-energy cosmic rays that whip around the galaxy. However, the solar wind also carries plasma and part of the sun’s magnetic field, which can crash into Earth’s magnetosphere and cause disturbances, including geomagnetic storms.

These storms occur when the sun experiences more turbulent activity, including solar flares and enormous expulsions of plasma into space, known as coronal mass ejections. Geomagnetic storms are responsible for spectacular aurora light shows that can be seen near the Earth’s poles, but at their most powerful, they can knock out a city’s power grid and potentially even disrupt global communications. Such events, while rare, can also be deadly to astronauts in space.

“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.”

Previous studies revealed that the sun’s magnetic field was somehow driving the solar wind, but researchers didn’t know the underlying mechanism. Earlier this year, Drake co-authored a paper which argued that the heating and acceleration of the solar wind is driven by magnetic reconnection—a process that Drake has dedicated his scientific career to studying.

The authors explained that the entire surface of the sun is covered in small “jetlets” of hot plasma that are propelled upward by magnetic reconnection, which occurs when magnetic fields pointing in opposite directions cross-connect. In turn, this triggers the release of massive amounts of energy.

“Two things pointing in opposite directions often wind up annihilating each other, and in this case doing so releases magnetic energy,” Drake said. “These explosions that happen on the sun are all driven by that mechanism. It’s the annihilation of a magnetic field.”

To better understand these processes, the authors of the new Nature paper used data from the Parker Solar Probe to analyze the plasma flowing out of the corona—the outermost and hottest layer of the sun. In April 2021, Parker became the first spacecraft to enter the sun’s corona and has been nudging closer to the sun ever since. The data cited in this paper was taken at a distance of 13 solar radii, or roughly 5.6 million miles from the sun.

“When you get very close to the sun, you start seeing stuff that you just can’t see from Earth,” Drake said. “All the satellites that surround Earth are 210 solar radii from the sun, and now we’re down to 13. We’re about as close as we’re going to get.”

Using this new data, the Nature paper authors provided the first characterization of the bursts of magnetic energy that occur in coronal holes, which are openings in the sun’s magnetic field as well as the source of the solar wind.

The researchers demonstrated that magnetic reconnection between open and closed magnetic fields—known as interchange connection—is a continuous process, rather than a series of isolated events as previously thought. This led them to conclude that the rate of magnetic energy release, which drives the outward jet of heated plasma, was powerful enough to overcome gravity and produce the sun’s fast wind.

By understanding these smaller releases of energy that are constantly occurring on the sun, researchers hope to understand—and possibly even predict—the larger and more dangerous eruptions that launch plasma out into space. In addition to the implications for Earth, findings from this study can be applied to other areas of astronomy as well.

“Winds are produced by objects throughout the universe, so understanding what drives the wind from the sun has broad implications,” Drake said. “Winds from stars, for example, play a crucial role in shielding planetary systems from galactic cosmic rays, which can impact habitability.”

This would not only aid our understanding of the universe, but possibly also the search for life on other planets.

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In addition to Drake, Marc Swisdak, a research scientist in UMD’s Institute for Research in Electronics and Applied Physics, co-authored this study.

Their paper, “Interchange reconnection as the source of the fast solar wind within coronal holes,” was published in Nature on June 7, 2023. 

This study was supported by NASA (Contract No. NNN06AA01C). This story does not necessarily reflect the views of this organization.

 

Original story by Emily C. Nunez: https://cmns.umd.edu/news-events/news/new-study-identifies-mechanism-driving-suns-fast-wind

The body’s cells are constantly receiving and reacting to signals from their environment. A lot is known about how a cell senses and responds to chemical signals, or biomolecules, such as COVID-19. But little is known about how signals from the physical environment, like touch, temperature or light, direct a cell’s activity. Understanding that process could lead to new ways of treating cancer and other disease.mage showing how the red mechano-chemical waves (actin waves) guide the signaling molecules (green). Image courtesy of UMD MURI team.

A new study published May 1, 2023 in the Proceedings of the National Academy of Sciences by a University of Maryland-led Multidisciplinary University Research Initiative (MURI) funded by the Air Force Office of Scientific Research has opened the door to seeing how cells react to physical signals.

“We elucidated a cell's sense of touch,” said Professor Wolfgang Losert, a team leader of the study. “We think how cells sense the physical environment may be quite distinct from how they sense the chemical environment. This may help us develop new treatment options for conditions that involve altered physical cellular environments, such as tumors, immune disease and wound healing.”

A major difference between chemical and physical signals is size. Chemical signals are 100,000 times smaller than the width of a human hair. Physical cues are the heavyweights in the ring.

“We looked at how cells sense crucial physical cues from their environment that are on the order of 100 times larger than chemical signaling molecules,” said Losert, who also has a joint appointment in UMD’s Institute for Physical Science and Technology (IPST).

“We’re really answering a kind of long-standing mystery of how cells react to cues in their environment that are on a physical rather than chemical-size scale,” said paper co-author and MURI team member John T. Fourkas, a professor in UMD’s Department of Chemistry and Biochemistry with a joint appointment in IPST.

The MURI team studied the major players in a cell’s interaction with its physical environment: the cytoskeleton, a network of proteins that surround a cell and acts as a direct sensor of the physical environment; actin, the protein that keeps cells connected; and the cell’s signaling pathways.

Qixin Yang (Ph.D. ’22, physics), who led the experiments and analysis for her Ph.D. research at UMD, said, “I think our work related to the cytoskeleton shows that it plays an important role in sensing physical cues, like pain.”

The MURI team found that the networks that guide cell migration are upstream for chemical sensing and downstream for physical, topographic sensing; and that actin is the direct sensor for both types of signals.

“I think this is the first real crucial confirmation that actin itself is the sensor and that the waves are really where they are in the sensing pathway, not way downstream, but up front and center,” Fourkas said.

“Our findings reveal that, in much the same way that patterns of waves in the ocean allow an expert surfer to understand the undersea topography, the so-called ‘mechano-chemical’ waves in cells are key in sensing signals from their physical environment that are much larger than single proteins,” Losert said. “That has implications for how you might design physical interventions to change the behavior of cells.”

For instance, previous research by a co-author of this study, Peter Devreotes of Johns Hopkins University, found that actin dynamics were different for cancer cells considered most invasive.

“Understanding how drugs impact waves is an important additional piece of information that may be used in making decisions on treatment options,” Losert said. “I see our study also providing pointers on how you can improve the ability of immune cells to be guided to their target.”

The MURI team is made up of researchers in physics, chemistry, biology, bioengineering and dermatology from the University of Maryland and several other institutions.

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In addition to Losert, Fourkas and Yang, UMD chemistry graduate student Matt Hourwitz was a co-author of the paper.

The paper, “Nanotopography modulates intracellular excitable systems through cytoskeleton actuation," was published in PNAS on May 1, 2023.

This research was supported by the Air Force Office of Scientific Research (Award No. FA9550-16-1-0052). This story does not necessarily reflect the views of this organization.

Original story by Ellen Ternes: https://cmns.umd.edu/news-events/news/afosr-muri-insight-how-cells-get-signals-physical-senses-could-lead-new-disease-treatments