SPACE/COSMOS
NJIT physicists trace sun’s magnetic engine, 200,000 kilometers below surface
Physicists report evidence that the solar dynamo — the magnetic engine powering the Sun’s 11-year cycles and eruptive events — operates nearly 200,000 kilometers beneath the Sun’s surface.
New Jersey Institute of Technology
image:
Diagram of the Sun’s interior and outer atmosphere, showing the core, radiative and convection zones — separated by the tachocline — and surface features such as sunspots, flares, the chromosphere and corona.
view moreCredit: NASA
Every eleven years, the Sun’s magnetic field flips. Sunspots — dark, cooler regions on the Sun’s surface that mark intense magnetic activity and often trigger solar eruptions —appear at mid-latitudes and migrate toward the star’s equator in a butterfly-shape pattern before fading as the cycle resets.
While this spectacle on the star’s surface has long been visible to astronomers, where this powerful cycle begins inside the star has remained hidden — until now.
Researchers at the New Jersey Institute of Technology (NJIT) analyzed nearly three decades of solar oscillation data to trace the Sun’s interior dynamics, and have now pointed to the likely location of the star’s magnetic engine deep beneath its surface — roughly 200,000 kilometers down, about the length of stacking 16 Earths end to end.
The findings, published in Nature Scientific Reports, provide one of the clearest observational windows yet into the Sun’s magnetic engine — the solar dynamo — shedding light on hidden forces shaping space weather patterns linked to the solar cycle, not only on Earth’s nearest star but potentially on other stars across the galaxy.
“Until now, we simply hadn’t heard enough from inside the star to be certain where the Sun’s intense magnetic fields are organized,” said Krishnendu Mandal, lead author and NJIT research professor of physics. “Sunspots are the visible footprints of magnetic fields that drive space weather on the Sun’s surface, but what solar oscillation data tells us is that the actual ‘engine room’ responsible for generating them originates much deeper.”
Sounding the Sun’s Interior Across Solar Cycles
To tune into the Sun’s interior, the team bridged roughly 30 years of observations from the Michelson Doppler Imager (MDI) on board NASA’s Solar and Heliospheric Observatory (SOHO) satellite, the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO), and the ground-based Global Oscillation Network Group (GONG).
The instruments have been recording sound waves generated by turbulent plasma motions within the star every 45 to 60 seconds since the mid-1990s.
By combining these observations, researchers analyzed billions of individual measurements, creating one of the longest and most detailed records of the Sun’s internal vibrations.
“Helioseismology is still a young field … reliable observations only began in the mid-1990s when GONG first came online,” Mandal explained. “Now, with nearly three 11-year solar cycles of data, we’re finally seeing clear patterns take shape that give us a window inside the star.”
Much like seismologists studying earthquakes on Earth, the researchers analyzed sound waves rippling through the Sun — measuring shifts in the waves’ travel times through the solar interior that reveal how hot plasma inside the star moves and rotates, exposing bands of faster and slower rotation beneath the surface.
The team's analysis revealed that these migrating rotation bands in the deep solar interior form a butterfly-shaped flow pattern, mirroring the sunspot migration that later emerges at the surface.
Analyzing these flow patterns through the interior pointed the team toward a critical transition layer nearly 200,000 kilometers beneath the surface — called the tachocline.
This thin boundary separates the Sun’s turbulent outer convection zone — where plasma churns and rises — from its stable radiative interior below. Across the tachocline, the Sun’s rotation changes abruptly, generating powerful shearing flows capable of powering the Sun’s magnetic fields.
“Rotation bands originating from magnetic structural changes near the Sun's tachocline can take several years to propagate to the surface,” Mandal said. “Tracking these internal changes gives us a clearer picture of how the solar cycle unfolds.”
The revealed correlation between the flow patterns across all three instruments and the degree to which they match the surface sunspot migration shows a clear connection between dynamics in the deep solar interior and solar activity on a global scale.
“For years, we suspected the tachocline was important for the solar dynamo, but now we have clear observational evidence,” Mandal said.
Clarifying where the dynamo operates could help scientists refine models used to forecast solar activity. Powerful solar eruptions — including flares and coronal mass ejections — can disrupt satellites, communications systems, navigation signals and power grids on Earth.
“While our findings do not yet enable precise predictions of future solar cycles, they highlight the importance of including the tachocline in space weather prediction models,” Mandal said. “Many current simulations account for processes only on near-surface layers, but our results show the entire convection zone, especially the tachocline, must be considered.”
The findings may also have implications beyond the Sun.
“Many stars exhibit magnetic cycles similar to the Sun's, but the high-resolution data achievable for the Sun due to its proximity to Earth is unattainable for others,” Mandal said. “Understanding the solar dynamo gives us a framework to study magnetic activity in other stars across the galaxy.”
The team at NJIT’s Center for Computational Heliophysics, led by study co-author and NJIT Distinguished Professor Alexander Kosovichev, plans to extend the team’s analysis and numerical simulations to refine their understanding of how the dynamo evolves and drives solar activity.
“There’s still much we don’t know about how the Sun’s internal magnetism evolves,” Mandal said. “With longer datasets and better observations, we hope to track these patterns across this and future solar cycles, potentially giving us better forecasts of space weather that can affect our daily life.”
The study, Helioseismic Evidence that the Solar Dynamo Originates Near the Tachocline, was supported by funding from NASA, including a grant “Consequences Of Fields and Flows in the Interior and Exterior of the Sun” from the NASA DRIVE Science Center — a collaboration of 13 U.S. universities and research centers that includes NJIT among its contributing institutions.
Article Title
Helioseismic evidence that the solar dynamo originates near the tachocline
New model to forecast space weather on way
image:
A coronagraph image with a large solar storm detected and tracked by the software in colour.
view moreCredit: Aberystwyth University
New efforts to forecast space weather with greater accuracy and reliability are being led by Aberystwyth University academics.
The scientists are aiming to shed new light on the workings of the Sun’s magnetic field, particularly within its outer atmosphere, known as the corona.
A longstanding and major scientific challenge, unlocking the corona’s secrets could help predict events like solar storms and eruptions, which can disrupt satellites, power grids and global communications systems.
By improving the depiction of the Sun’s magnetic field, the enhanced maps generated by the project will significantly boost the precision of space weather predictions - especially in pinpointing the timing of disruptive solar events that affect Earth.
Professor Huw Morgan from Aberystwyth University’s Department of Physics is leading the project. He said:
“Current models of the Sun’s magnetic field rely solely on data from the Sun’s surface, but the corona remains a mystery in many ways.
“This project will harness data from coronagraphs - special instruments that block out the Sun’s intense light - to reveal the Sun’s outer atmosphere. By studying patterns in this data, we will be able to adapt existing models and offer the scientific community and space weather forecasters a more accurate picture of the Sun’s magnetic field.
“This has important implications not just for scientific research, but for operational forecasting at institutions like the UK Met Office. Improved forecasting will help infrastructure operators to act to mitigate the problems caused on Earth by solar activity.”
The project, ‘CorMag: A magnetic model of the corona with upper boundary observational constraints’ is funded by the Science and Technology Facilities Council.
A spectacular eruption from the Sun.
Credit
Aberystwyth University
Asteroid Bennu's rugged surface baffled NASA. We finally know why
image:
Close-up of a sample particle from asteroid Bennu.
view moreCredit: NASA/Scott Eckley
In one of the biggest surprises of NASA's OSIRIS-REx mission, its target asteroid, Bennu, turned out to be a jagged, rugged world covered in large boulders, with few of the smooth patches that earlier observations from Earth-based instruments had indicated.
"When OSIRIS-REx got to Bennu in 2018, we were surprised by what we saw," said Andrew Ryan, a scientist with the University of Arizona Lunar and Planetary Laboratory, who led the mission's sample physical and thermal analysis working group. "We expected some boulders, but we anticipated at least some large regions with smoother, finer regolith that would be easy to collect. Instead, it looked like it was all boulders, and we were scratching our heads for a while."
Particularly puzzling were observations made in 2007 by NASA's Spitzer Space Telescope, which measured low thermal inertia, indicative of an asteroid whose surface heats up and cools down rapidly as it rotates into and out of sunlight, like a sandy beach on Earth. This was at odds with the many large boulders that OSIRIS-REx found upon arrival, which should act more like blocks of concrete, shedding heat long after the Sun has set.
Data collected by the OSIRIS-REx spacecraft during its survey campaign at the asteroid suggested a possible explanation: the boulders could be much more porous than expected. Once the samples were delivered to Earth, researchers were able to investigate this further.
Ryan's team scrutinized rock particles collected from Bennu's surface using a variety of laboratory analysis techniques. In a study published in Nature Communications, the authors reported that the boulders are indeed porous enough to account for some of the observed heat loss, but not all of it. Rather, many of the rocks turned out to be riddled with extensive networks of cracks.
To test whether the cracks could be the reason for the asteroid’s surface losing heat, a team at Nagoya University in Japan analyzed Bennu sample material using lock-in thermography. This laser-based technique allows researchers to hit a tiny spot on the surface of the sample and measure how the heat diffuses through it, similar to how ripples move across a pond.
"That's when things became really interesting," Ryan said. "The thermal inertia measured in the lab samples turned out to be much higher than what the spacecraft's instruments had recorded, echoing similar findings obtained by the team of OSIRIS-REx's partner mission, JAXA's (Japan Aerospace Exploration Agency) Hayabusa-2."
To make meaningful predictions about how the material would behave in the large boulders on the asteroid, the team had to find a way to scale up the measurements obtained with the small sample particles.
Using a glove box, team members at NASA's Johnson Space Center in Houston sealed sample particles in air-tight containers under a protective nitrogen atmosphere, then transferred them to a lab where they could perform X-ray computed tomography, or XCT scans. Once a particle was scanned, it went back into the glove box.
"The sample goes into its own 'spacesuit,' gets a CT scan, and then comes back to its pristine environment, all without having any exposure to the terrestrial environment," said Nicole Lunning, lead OSIRIS-REx sample curator within the Astromaterials Research and Exploration Science division at NASA Johnson and one of the study's co-authors. "We can image right through these airtight containers to visualize the shape and internal structure of the rock that's inside."
"X-ray computed tomography allows us to look at the inside of an object in three dimensions, without damaging it," said study co-author and NASA Johnson X-ray scientist Scott Eckley.
Once mapped in this way, a permanent three-dimensional digital archive of a sample particle's shape and interior is created, and the data are entered into a public database. Ryan's team used the X-ray CT scan data for computer simulations modeling heat flow and thermal inertia. When scaled up to boulder size, the thermal inertia results fell into agreement with what the spacecraft had measured at the asteroid.
Where scientists once expected the boulders of Bennu to be extremely porous and fluffy, perhaps even spongy, the sample analysis revealed something unexpected.
"It turns out that they're really cracked too, and that was the missing piece of the puzzle," Ryan said.
Ron Ballouz, a scientist with the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, and the paper's second author, said this work transforms how scientists interpret the structure of an asteroid based on its thermal properties seen from Earth.
"We can finally ground our understanding of telescope observations of the thermal properties of an asteroid through analyzing these samples from that very same asteroid," Ballouz said.
Journal
Nature Communications
Article Title
Low thermal inertia of carbonaceous asteroid Bennu driven by cracks observed in returned samples
Article Publication Date
17-Mar-2026
The same particle analyzed with X-ray computed tomography scanning. This specimen shows the most common types of crack networks observed in Bennu samples. One has an extensive and connect framework of curved cracks, whereas the other has sparse, straight and flat fractures.
Credit
NASA/Scott Eckley
From dust to planets: a turbulent story
image:
Dr. Holly L. Capelo, Physics Institute, Space Research & Planetary Sciences (WP), University of Bern and NCCR PlanetS
view moreCredit: Courtesy of Holly Capelo
Planets form within protoplanetary disks: vast disks of gas and dust orbiting around very young stars. From the finest dust grains to fully-formed planets, several distinct physical processes occur. At one end, the fine dust particles collide and clump together electrostatically, growing in size up to a few millimeters. At the other, planetesimals – rocky or icy bodies of a few hundred meters to a few kilometers in size – collide, merge and aggregate, slowly growing into rocky or icy planets, and for the fastest ones eventually accreting gas to become giants. In between, however – from centimeter-sized to hundred meter-sized boulders – most planet-forming scenarios hit a "barrier" that prevents further growth. At these sizes, clumps tend to bounce off each other, break up in the collision process, or even evaporate when drifting too close to their star. This barrier has puzzled scientists for decades.
Since the turn of the century, however, theoretical models have proposed an additional mechanism that could fill the gap. Because the gas-dust mixture behaves like a fluid, various hydrodynamical instabilities can develop in it and cause the dust to clump into denser clouds, leading for the largest ones to eventually form planetesimals. Each of these instabilities arises under specific conditions and in different regions of the disk, and can affect it in distinct ways. One of these instabilities suspected to play an essential role is the shear-flow instability, which occurs at the interface between two fluids with different properties – in this case mainly velocity and density. However, whether such shear-flow instabilities really occur or not under the extremely tenuous gas conditions in protoplanetary disks had never been proven experimentally. Using a unique experiment that exploits the micro-gravity conditions during parabolic or "0g" flights, a team led by Dr. Holly L. Capelo from the Space Research and Planetology Division at the Physics Institute of the University of Bern has now shown experimentally that shear-flow instabilities can indeed form – even in extremely thin gas. The study has just been published in Communications Physics.
Flying an experiment in zero gravity
To investigate these flow instabilities which can, depending on the exact conditions, either foster or hinder dust clumping into planetesimals the team around Capelo started developing the TEMPus VoLA experiment in 2020, with a one-of-a-kind instrument at its core. Funded by the NCCR PlanetS and the Swiss Space Office, it was designed and assembled at the University of Bern, in collaboration with the University of Zurich and ETH Zurich. The instrument is equipped with high-speed cameras that track the behavior of dust particles in an extremely thin gas under vacuum conditions. It was built specifically for parabolic flights, a special type of flight that provides micro-gravity. "On Earth, gravity influences the behavior of the dust and gas," explains Prof. Lucio Mayer from the University of Zurich "Only conditions that simulate the absence of gravity allow us to probe an extremely dilute flow regime, similar to the gas and dust disks orbiting around young stars." During parabolic flights, a specially adapted aircraft follows a trajectory in which it repeatedly climbs and dives at angles of about 45 degrees. Each dive phase provides weightlessness for around 20 seconds, while the climb simulates stronger gravity than on Earth. During several flight campaigns from the UZH Space Hub and the European Space Agency (ESA), the team systematically refined and varied the conditions of the experiment to test when shear-flow was triggered. "To sum up, we recreated the conditions that arise in the planet-forming regions of protoplanetary discs, and we managed to demonstrate that this theoretically proposed shear-flow instability is not just a mathematical construct, but can actually occur in reality," explains Capelo.
However, parabolic flights only offer very short phases of weightlessness. "Once the instability starts, we noticed characteristic patterns developing in the flow of the material. Yet, the limited micro-gravity time prevents us from observing how these patterns evolve into fully developed turbulence," explains Capelo. The team is therefore developing a more advanced version of the experiment to operate on a space station such as the International Space Station (ISS). There, much longer periods in micro-gravity would allow turbulence to be observed, adding another crucial piece to the puzzle of planet formation.
To the origins of the Solar System
To understand how planetary systems form, astronomers rely on a range of elements. Modern telescopes can observe the protoplanetary disks orbiting a star, and determine the properties of the gas and dust within it and understand their global evolution by studying disks of different ages. On the theory side, computer simulations describe mathematically and physically the disk evolution and planet formation. None of them, however, has yet the capacity to study disks with a resolution high enough to distinguish the smallest structures within it. "In our Solar System, comets and asteroids bear witness of the early stage of our system and provide clues to the composition and structure of planetesimals, but we still cannot probe their early evolution," says Dr. Antoine Pommerol of the University of Bern. "Only experiments can bridge this knowledge gap and reveal the crucial details of the dust and gas movement on spatial and time scales so small that they cannot be observed directly in the cosmos." The new experiment not only provides a direct confirmation that a long-theorized phenomenon can occur under protoplanetary disk-like conditions, it will also help to improve theoretical models and refine simulations. "This, in turn, will lead to a better understanding of the overall picture of planetary systems formation – and ultimately how our own Solar System, and Earth itself, formed billions of years from a simple cloud of dust and gas", says Capelo.
The fruits of national collaboration across Switzerland
"Bringing such a pioneering experiment to life was a major challenge," says Capelo. While the NCCR PlanetS funded the initial development of the project, each participating institution contributed a unique expertise to it: from the instrument building proficiency of the University of Bern, to the planet formation theory knowledge of the University of Zurich, and the experience of the ETH Zurich in the observation and laboratory analysis of small solar system bodies.
The expertise of the UZH Space Hub, ESA/PRODEX programs, and Novespace in preparing and conducting parabolic flights was also a key component of the project. "Overall, the ability of Swiss institutions to join forces efficiently and collaborate closely on this project led to its remarkable success and to breakthroughs in the investigation of the fundamental physics of planet formation. These results pave the way to hopefully observe such mechanisms operating in the cosmos," concludes Capelo.
Bernese space exploration: With the world’s elite since the first moon landing
When the second man, "Buzz" Aldrin, stepped out of the lunar module on July 21, 1969, the first task he did was to set up the Bernese Solar Wind Composition experiment (SWC) also known as the “solar wind sail” by planting it in the ground of the moon, even before the American flag. This experiment, which was planned, built and the results analyzed by Prof. Dr. Johannes Geiss and his team from the Physics Institute of the University of Bern, was the first great highlight in the history of Bernese space exploration.
Ever since Bernese space exploration has been among the world’s elite, and the University of Bern has been participating in space missions of the major space organizations, such as ESA, NASA, and JAXA. With CHEOPS the University of Bern shares responsibility with ESA for a whole mission. In addition, Bernese researchers are among the world leaders when it comes to models and simulations of the formation and development of planets.
The successful work of the Department of Space Research and Planetary Sciences (WP) from the Physics Institute of the University of Bern was consolidated by the foundation of a university competence center, the Center for Space and Habitability (CSH). The Swiss National Fund also awarded the University of Bern the National Center of Competence in Research (NCCR) PlanetS, which it manages together with the University of Geneva.
Videos of the TEMPus VoLA parabolic flights and interviews of its main participants:
https://www.youtube.com/watch?v=m79EEBrgTsY
youtube.com/watch?v=tDR2DWsKsdk&embeds_referring_euri=https%3A%2F%2Fmediarelations.unibe.ch%2F&source_ve_path=OTY3MTQ
https://www.youtube.com/watch?v=tDR2DWsKsdk
Journal
Communications Physics
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Experimental evidence for granular shear-flow instability in the Epstein regime
Article Publication Date
17-Mar-2026
Sharper LEO navigation through outer-loop framework
As demand grows for reliable positioning beyond conventional Global Navigation Satellite Systems (GNSS), researchers are turning to Low Earth Orbit (LEO) satellites as a promising backup. In the new study, a team developed an outer-loop positioning framework that explicitly accounts for signal propagation time in LEO Doppler observations—an often overlooked factor in signal-of-opportunity navigation. By introducing a geometric propagation-time model into the observation process, the method improved three-dimensional position and velocity estimation while also producing more stable receiver clock corrections. The advance points toward more dependable navigation in dense cities, transport corridors, and other environments where traditional satellite positioning can struggle.
Positioning, navigation, and timing services are now essential for autonomous systems, logistics, and mass-market electronics, yet conventional GNSS remains vulnerable in urban canyons, tunnels, and other obstructed environments. LEO constellations such as Starlink, OneWeb, and Iridium have drawn growing interest because their signals are strong, plentiful, and fast-moving, making them attractive as backup or complementary navigation sources. But unlike GNSS satellites, many LEO platforms do not provide transmission timestamps or pseudorange-style observables, leaving signal propagation time uncertain. Previous studies have focused heavily on orbit-related errors, while the role of propagation time in state estimation has received far less attention. Based on these challenges, deeper research into propagation-time-aware LEO positioning is needed.
In 2026, researchers from the Universitat Autònoma de Barcelona reported (DOI: 10.1186/s43020-026-00189-w) in Satellite Navigation a new outer-loop positioning framework for LEO Doppler observations that explicitly accounts for signal propagation time, demonstrating improved accuracy and stability in both simulations and real Iridium measurements.
The proposed method combines an outer loop and an inner loop to better reconstruct the true geometry of LEO signal transmission. In the outer loop, satellite states are updated with TLE+SGP4, predicted Doppler observations are generated, and residuals are estimated through weighted least squares. In the inner loop, intermediate quantities—especially signal propagation time—are iteratively refined. The framework also introduces a finite-difference Doppler observation model that reduces the influence of atmospheric delay and better links Doppler drift to receiver position, velocity, and clock states. Experiments showed that the algorithm improved three-dimensional position accuracy by more than 15% and velocity accuracy by more than 25%, while significantly improving clock-related error estimation. In measured Iridium observations, point-positioning error fell by 13.4% compared with an existing coarse-time approach, and solution stability also improved. The study further identified a practical convergence limit: when the initial position error reaches 200 km, the tolerable receiver clock error drops below 50 ms, underscoring the importance of good initialization in real deployments.
The findings suggest that propagation time is not merely a secondary correction in LEO navigation, but a central factor that shapes the quality of the final solution. By treating it explicitly rather than absorbing it into a rough coarse-time estimate, the researchers showed that Doppler-based positioning can become both more accurate and more robust. The work also provides a clearer understanding of how spatial and timing uncertainties interact, offering valuable guidance for future receiver design and algorithm development.
The broader implications are considerable. As LEO constellations continue to expand, propagation-time-aware positioning could help build resilient navigation services for GNSS-challenged or GNSS-denied environments. The approach may prove especially useful for low-cost devices, mobile platforms, and Internet-of-Things applications that cannot rely on high-end atomic timing hardware. While further validation under more diverse real-world conditions will still be needed, this study establishes a practical and theoretically grounded route toward more accurate, stable, and scalable LEO-based navigation services in the years ahead.
###
References
DOI
Original Source URL
https://doi.org/10.1186/s43020-026-00189-w
Funding information
This work has been partly supported by the Spanish Agency of Research (AEI) under grant PID2023-152820OB-I00 funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU, AEI grant PDC2023-145858-I00 funded by MICIU/AEI/10.13039/501100011033 and by the European Union NextGeneration EU/PRTR, the AGAUR-ICREA Academia Program, and the Departament de Recerca i Universitats de la Generalitat de Catalunya under grant 2021 SGR 00737.
About Satellite Navigation
Satellite Navigation (E-ISSN: 2662-1363; ISSN: 2662-9291) is the official journal of Aerospace Information Research Institute, Chinese Academy of Sciences. The journal aims to report innovative ideas, new results or progress on the theoretical techniques and applications of satellite navigation. The journal welcomes original articles, reviews and commentaries.
Journal
Satellite Navigation
Subject of Research
Not applicable
Article Title
An innovative outer-loop positioning framework for LEO Doppler observations considering propagation time
Article Publication Date
10-Mar-2026
No comments:
Post a Comment