New Study Identifies Mechanism Driving the Sun’s Fast Wind

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. 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.


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:

Insight into How Cells Get Signals from Physical Senses Could Lead to New Disease Treatments

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.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.


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:


New Research Sheds Light on How Mesothelioma Develops

Mesothelioma has been a high-profile disease at the center of several multi-billion-dollar lawsuits, but the disease itself remains a medical mystery. 

The incurable cancer develops on the lining of many internal organs—including the lungs and peritoneum—but its symptoms are often undetectable until about 40 years after initial exposure to asbestos, a common and naturally occurring mineral. This long latency period, as well as cases of mesothelioma in individuals who have no known exposure to asbestos, has made the disease and its origins a longstanding puzzle to doctors and scientists alike. 

Now, an interdisciplinary team of researchers from the University of Maryland may have identified an essential piece of the puzzle. In a paper published online in the journal Environmental Research in January 2023, the team suggests that the key to understanding mesothelioma lies in how immune cells “sense” and interact with particles around them. 

According to the new study, the shape and size of contaminant particles, like asbestos fibers, significantly influence how the immune system responds after exposure—ultimately impacting health outcomes.An asbestos fiber (stained blue) in lung tissue being surrounded by macrophages. Image courtesy of the Centers for Disease Control and Prevention.An asbestos fiber (stained blue) in lung tissue being surrounded by macrophages. Image courtesy of the Centers for Disease Control and Prevention.

“The geometry or size of a particle is more important than its mineral composition when it comes to how likely it is to cause adverse health effects in patients,” explained study co-author and UMD Professor Emerita of Geology Ann Wylie. “Asbestos kicks up an immune response when the immune system is exposed to the right shape and size of particle.”

“We believe that the most dangerous types of fibers—ones that are particularly thin and long—likely cause immune cells called macrophages to recruit other immune cells to asbestos exposure sites within tissue. This response prevents the immune cells from reaching other places where they’re needed, like precancerous lesions,” added study co-author Wolfgang Losert, a professor in the Department of Physics and the Institute for Physical Science and Technology at UMD. “This could cause the immune system to effectively ignore other serious conditions around that organ.”

In a previous study, some members of the research team found that mineral particles with diameters less than 250 nanometers and lengths greater than 5 micrometers were more difficult for the lungs to physically clear out than their shorter counterparts. The longer particles stayed in the lungs longer, further interacting with healthy lung tissues before eventually encountering immune cells like macrophages.

For the new study, the researchers examined particles taken from mineral samples from various geological sites. They found that immune cells used a mechanism called esotaxis to “sense” physical features—such as size, shape and texture—of the particles around them and responded differently to each particle based on that information. 

The researchers observed that when macrophages encountered these small and dangerous types of particles (including smaller asbestos fibers), the macrophages “activated” to recruit other immune cells to the site. However, because these longer particles are less able to be removed physically, activated macrophages continue to call for more immune cells to the same site over a long period of time, dominating immune cell communication.

The researchers hypothesize that this eventual “hijacking” of the immune cell migration system would lead to other nearby regions of an infected organ to be neglected because all immune cells are delegated to a single site. As a result, those other tissues would be deprived of the immune system’s healing abilities—a possible explanation as to why many immunocompromised patients can develop mesothelioma even without known exposure to asbestos fibers.

In essence, a particle’s nanotopography—their surface features formed at a nanoscopic level—indirectly controls the internal machinery that allows immune cells to move.

“This response basically overwhelms the immune cell communication system and diverts the body’s own defenses away from where they’re needed,” explained study co-author John Fourkas, a professor in the UMD Department of Chemistry and Biochemistry and the Institute for Physical Science and Technology. “The physical characteristics of a mineral particle can change the behavior of immune cells in the long term, which could be why mesothelioma symptoms take a minimum of 30 to 40 years to manifest.” 

The team believes that their theory also applies to mineral particles that are similar in size to carcinogenic asbestos fibers, which could provide more insight into other diseases caused by such particles. With rising concerns about the carcinogenic properties of airborne mineral particles like crystalline silica and carbon nanotubes, additional information about esotaxis and its effects on immune responses could be the key to protection. 

“More research about the induction of cancer by minerals is still needed—it’s complicated and requires the expertise of geologists, chemists, physicists and bioscientists,” Wylie said. “But this project and others like it bring us a step closer to figuring out what mechanisms underlie not only mesothelioma but all types of cancer formations.”


Original story:

Additional UMD co-authors on the paper include Shuyao Gu, Abby Bull, Amilee Huang, Matt Hourwitz and Mona Abostate.

The study, “Excitable systems: A new perspective on the cellular impact of elongate mineral particles,” was published in Environmental Research on January 23, 2023.

This research was supported by the National Science Foundation (Award No. PHY2014151). This story does not necessarily reflect the views of this organization.

Experiment Demonstrates Continuously Operating Optical Fiber Made of Thin Air

Researchers at the University of Maryland have demonstrated a continuously operating optical fiber made of thin air.

The most common optical fibers are strands of glass that tightly confine light over long distances. However, these fibers are not well-suited for guiding extremely high-power laser beams due to glass damage and scattering of laser energy out of the fiber. Additionally, the need for a physical support structure means that glass fiber must be laid down long in advance of light signal transmission or collection.

Professor Howard Milchberg and his group in the Depts. of Physics, ECE, and the Institute for Research in Electronics and Applied Physics at the University of Maryland have demonstrated an optical guiding method that beats both limitations, using auxiliary ultrashort laser pulses to sculpt fiber optic waveguides in the air itself. These short pulses form a ring of high-intensity light structures called “filaments”, which heat the air molecules to form an extended ring of low-density heated air surrounding a central undisturbed region; this is exactly the refractive index structure of an optical fiber. With air itself as the fiber, very high average powers can potentially be guided. And for collection of remote optical signals for detecting pollutants and radioactive sources, for example, the air waveguide can be arbitrarily “unspooled” and directed at the speed of light in any direction.An unguided continuous wave green laser beam (left), and the same beam guided by an air waveguide generated at 10 Hz (center) and at 1000 Hz (right). The air waveguide on the right is essentially continuously operating.An unguided continuous wave green laser beam (left), and the same beam guided by an air waveguide generated at 10 Hz (center) and at 1000 Hz (right). The air waveguide on the right is essentially continuously operating.

In an experiment published in January in Physical Review X [Physical Review X 13, 011006 (2023)], graduate student Andrew Goffin and colleagues from Milchberg’s group showed that this technique can form 50-meter-long air waveguides that persist for tens of milliseconds until they dissipate from cooling by the surrounding air. Generated using only one watt of average laser power, these waveguides could theoretically guide megawatt average power laser beams, making them exceptional candidates for directed energy. The waveguide method is straightforwardly scalable to 1 kilometer and longer. However, the waveguide-generating laser in that work fired a pulse every 100 milliseconds (repetition rate of 10 Hz), with cooling dissipation over 30 milliseconds, leaving 70 milliseconds between shots with no air waveguide present. This is an impediment to guiding a continuous wave laser or collecting a continuous optical signal.

In a new Memorandum in Optica [Optica 10, 505 (2023)], Andrew Goffin, Andrew Tartaro, and Milchberg show that by increasing the repetition rate of the waveguide-generating pulse up to 1000 Hz (a pulse every millisecond), the air waveguide is continuously maintained by heating and deepening the waveguide faster than the surrounding air can cool it. The result is a continuously operating air waveguide that can guide an injected continuous wave laser beam. Because the waveguide is deepened by repetitive generation, guided light confinement efficiency improves by a factor of three at the highest repetition rate.

Continuous wave optical guiding significantly improves the utility of air waveguides: it increases the maximum average laser power one can transport and maintains the guiding structure for use in continuous collection of remote optical signals. And because kilometer-scale and longer waveguides are wider, cooling is slower and a repetition rate well below 1 kHz will be needed to maintain the guide. This more lenient requirement makes continuous air waveguiding over kilometer and longer ranges easily achievable with existing laser technology and modest power levels.

“With an appropriate laser system for generating the waveguide, long-distance continuous guiding should be easily doable”, says Goffin, “Once we have that, it’s just a matter of time before we’re transmitting high power continuous laser beams and detecting pollutants from miles away.”

(Possibly) Breaking the Standard Model, One Lepton-universality-violating Decay at a Time

Physicists in general, and high energy physicists in particular, like to "break" things. It can be useful to prove again that a well established theory is true, especially if you are probing a yet-untested prediction of the venerable theory. But proving that the theory is wrong--or at least not completely true--that is where the fun is. This is why a series of measurements of b hadron decays that seemingly break the Standard Model (SM) of particle physics is garnering so much excitement.

You see, the SM is the most well established theory of them all, the only one with predictions corroborated to the 11th digit (see the anomalous magnetic moment of the electron). It was fully fleshed out in the 70's, and since then it has racked up success after success. Its crowning achievement came in 2012 when the long-predicted Higgs boson was finally confirmed to be alive and well. Despite this resiliency, the SM is not the end of it all. It can't explain why the mass of the Higgs is so low, what the nature of dark matter is, or why there is so much more matter than antimatter in the universe. Finding answers to these questions will thus require breaking, or extending, the SM.

Enter Lepton Flavor Universality (LFU) violation. LFU is a fundamental assumption within the SM involving the three lepton flavors: electron, muon, and tau. All SM interactions other than the Higgs are assumed to be flavor universal, and this has been shown to be true in numerous measurements. Since 2012, however, an intriguing pattern has emerged in decays of b hadrons (particles with a b quark inside) to final states with a c quark, a tau lepton τ, and a neutrino ν. When results involving a tau lepton and a neutrino are compared to decays involving a muon or an electron and a neutrino, they tend to be higher than we'd expect from SM calculations. This is shown in the nearby figure by all the measurements keeping their distance from the theoretical predictions in blue. Measurements that measured the two LFU quantities RD and RD* are shown as Artistic representation of a proton-proton collision resulting in a B meson that subsequently decays to a charmed D0 or D* meson, a tau lepton, as well as a smaller antineutrino. Credit: Greg Stewart, SLAC National Accelerator Laboratory/BaBar and Manuel Franco Sevilla.Artistic representation of a proton-proton collision resulting in a B meson that subsequently decays to a charmed D0 or D* meson, a tau lepton, as well as a smaller antineutrino. Credit: Greg Stewart, SLAC National Accelerator Laboratory/BaBar and Manuel Franco Sevilla.ellipses while measurements of RD* alone are shown as markers with uncertainties.
None of these results on their own rises to what is typically known as an "observation" (5σ statistical significance), and it could very well go away. For instance, a similar pattern that had appeared when comparing decays involving a kaon and two muons to decays with a pair of electrons was recently shown to be an artifact  of an underestimated background. But the consistency among results that share the same b→ cτν underlying process is very suggestive. Multiple explanations have been proposed that would explain all of these with physics beyond the SM (BSM). A particularly neat solution postulates a new kind of exotic particle that interacts with both leptons and quarks: a vector leptoquark. 
In an article published last year in Review of Modern Physics ("Semitauonic b-hadron decays: A lepton flavor universality laboratory"), my co-authors and I comprehensively described these results, delved into the main sources of uncertainty, and mapped out the future measurements. Spoiler alert: while we do not know whether BSM physics will be discovered, we are rather confident that we will know whether these results are due to BSM physics or not within 5-10 years. 
And the first of these new results was just submitted to Physical Review Letters  Professor Hassan Jawahery and Dr. Phoebe Hamilton, together with Dr. Greg Ciezarek from CERN, measured for the first time RD and RD* simultaneously at LHCb. The uncertainties are still large, so it is hard to say whether the discrepancy will be proven true. But this result sets the stage for another meaThe results reflect analysis of two years of data by Phoebe Hamilton and Hassan Jawahery and their CERN collaborator, Greg Ciezarek.The results reflect analysis of two years of data by Phoebe Hamilton and Hassan Jawahery and their CERN collaborator, Greg Ciezarek.surement based on the same techniques that uses a data sample more than 6 times larger. This work, carried out by the all-UMD team Professor Manuel Franco Sevilla, Dr. Hamilton, Dr. Christos Hadjivasiliou, Yipeng Sun, and Alex Fernez, is now fairly advanced. So stay tuned, there's potential for SM-breaking ahead!

 --Manuel Franco Sevilla