Scientists Map Giant Plasma Tides Beneath Sun’s Surface, Revealing Hidden Dynamics

The NSSL, extending about 35,000 km beneath the Sun’s surface, is a region where rotational dynamics undergo dramatic transitions.

An international team of solar physicists has successfully traced vast tides of plasma beneath the Sun’s surface in a critical region known as the near-surface shear layer (NSSL). These giant, dynamic flows shift in sync with the Sun’s magnetic heartbeat and could significantly influence space weather patterns that impact satellites, communication networks, and power grids on Earth.

The NSSL, extending about 35,000 km beneath the Sun’s surface, is a region where rotational dynamics undergo dramatic transitions. The layer is marked by variations in the Sun’s rotation rate with depth, a complex dance that changes over time and spatial scales, and correlates strongly with solar magnetic activity, including the 11-year sunspot cycle.

Peering Into the Sun’s Inner Weather

This groundbreaking study, led by researchers from the Indian Institute of Astrophysics (IIA), an autonomous institute under India’s Department of Science and Technology (DST), in collaboration with scientists from Stanford University and the National Solar Observatory (NSO), USA, offers an unprecedented glimpse into the Sun’s "inner weather."

Published recently in the prestigious journal The Astrophysical Journal Letters, the research employs cutting-edge helioseismology — a technique that uses sound waves traveling through the Sun’s interior to reveal hidden movements.

Utilizing over a decade of data collected by NASA’s Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) and ground-based observations from NSO’s Global Oscillations Network Group (GONG), the researchers meticulously tracked plasma currents deep beneath the surface.

Stunning Discoveries of Plasma Flow Patterns

Under the leadership of Professor S.P. Rajaguru and PhD student Anisha Sen from IIA, the team uncovered striking patterns: surface plasma flows tend to converge toward latitudes teeming with sunspots. However, halfway through the NSSL, these currents dramatically reverse direction, flowing outward and forming large-scale circulation cells.

These findings highlight the critical role of the Coriolis force—the same force that spins hurricanes on Earth—in shaping solar plasma movements. As plasma converges and diverges, the Coriolis effect twists these flows, influencing the Sun’s rotational dynamics by modifying rotational shear, or the gradient of rotation across depths.

Curiously, the study found that these local plasma currents are distinct from the Sun’s larger-scale zonal flows, known as torsional oscillations. These oscillations, giant belts of slower and faster rotation that ripple through the Sun’s interior, appear to be driven by deeper, still-unknown forces.

A Deep Dive into Sunspot Dynamics

To validate their global observations, the researchers performed high-resolution, localized studies of major sunspot regions using sophisticated 3D velocity mapping techniques. The localized data remarkably matched the broader flow patterns, showing clear evidence of surface inflows and deeper outflows around sunspot zones.

“This is a stunning look into how the Sun’s inner weather patterns form and evolve,” commented Professor S.P. Rajaguru. “Understanding these hidden flows is crucial, not just for theoretical modeling, but also for practical reasons: solar activity influences space weather events that can cause serious disruptions here on Earth.”

Lead author Anisha Sen added, “By zooming in on sunspot regions with 3D velocity maps, we confirmed that these plasma flows behave consistently from global to local scales, helping build confidence in our models.”

The study also included contributions from researcher Abhinav Govindan Iyer and international collaborators, emphasizing the global importance of solar research in our increasingly technology-dependent world.

Toward More Accurate Space Weather Forecasting

These new insights into the dynamics of the NSSL suggest that while the Sun’s outer layers show fascinating and organized plasma patterns, there may be deeper, still-hidden layers whose behaviors are key to driving the Sun’s global magnetic and rotational dynamics.

The ability to better understand and predict the Sun’s behavior is crucial. Solar storms, massive ejections of magnetic energy and plasma, can have severe consequences for modern infrastructure, including satellite operations, radio communications, and even electrical grids.

This research is a significant step forward toward developing realistic models that can predict solar activity with greater accuracy, thereby safeguarding critical Earth-based technologies.

The findings also open new frontiers in the field of stellar physics, offering a framework for understanding other stars' magnetic and rotational behaviors by analogy to our own Sun.