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NASA’s COFFIES Science Center Makes Breakthrough on Solar Enigma

Researchers are closer to unraveling a long-standing solar mystery surrounding the extreme thinness of the Sun’s tachocline layer — a region critical for creating space weather.

One of NASA’s DRIVE (Diversify, Realize, Integrate, Venture, Educate) Science Centers, COFFIES (Consequences Of Fields and Flows in the Interior and Exterior of the Sun), enabled a group of researchers to tackle a fundamental question about how the Sun works in a recent paper.

Our star consists of various layers that generate magnetic fields through a process called the solar dynamo. This magnetic engine powers solar activity, sparking solar flares and coronal mass ejections that dictate space weather cycles. Investigating these cycles is vital, as space weather can impact astronaut safety, satellite communications, and global navigation systems.

A round, colorful cutaway of the Sun identifying different elements: Differential Rotation, Tachocline, Near Surface Shear Layer, Convection, Flux Emergence, Acoustic Waves, Active Region, Surface Velocity, Meridional Circulation
A cutaway graphic of the Sun to show the different processes occurring within and on the Sun. The Sun’s dynamic activity arises from several interconnected processes. Active regions, marked by strong magnetic fields and sunspots, are sources of solar flares and coronal mass ejections, often forming due to the emergence of magnetic flux from the solar interior. The Sun’s differential rotation, where the equator spins faster than the poles, stretches and twists these magnetic fields. Meridional circulation, a north-south plasma flow, further transports these fields across the solar surface. Convection, the heat transfer mechanism in the Sun’s interior, creates crucial plasma movements. Near the surface, a shear layer exhibits changing rotation speeds with depth, influencing magnetic field dynamics. Deep within, the tachocline, a transition zone between uniform and differential rotation, is vital for the generation of the Sun’s magnetic field. Finally, acoustic waves, generated by surface turbulence, allow scientists to probe the Sun’s internal structure.
COFFIES DRIVE Science Center

The tachocline, sandwiched between the Sun’s radiative and convective zones, is essential to these space weather cycles. The tachocline is believed to serve as the main amplifier of the magnetic field, storing, organizing, and releasing magnetic energy that eventually emerges at the solar surface as sunspots. Emerging sunspot regions trigger space weather events. Deciphering the tachocline’s formation and function enhances predictive space weather modeling.

The tachocline’s extreme thinness long remained a mystery, as earlier science models failed to replicate its unique and fluid behavior. The COFFIES team refined state-of-the-art computer models to produce a scenario that reveals where the tachocline is essential in driving the solar dynamo, while a fluctuating magnetic field is key for keeping the tachocline’s signature thinness.

A colorful orb sits in the middle. A cutaway with black lines show red, orange, and white lines on the outer layer of the orb, with darker reds, oranges, yellows, and dark blues in the center.
This scientific visualization shows the complex fluid dynamics and magnetic interactions in the Sun’s interior zones. The cutaway view highlights the plasma flows and magnetic fields that work together to contain this extremely thin layer, called the tachocline.
COFFIES DRIVE Science Center

These findings and methodologies were recently published in The Astrophysical Journal.

By Desiree Apodaca
NASA’s Goddard Space Flight Center, Greenbelt, Md.

NASA's Heliophysics Missions Communications Lead