The Sun’s magnetic sngine has been found — 200,000 kilometers below Its surface

The study, published in Scientific Reports, draws on nearly 30 years of helioseismic data collected by three complementary instruments: the Michelson Doppler Imager (MDI) aboard NASA’s Solar and Heliospheric Observatory (SOHO), the Helioseismic and Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO), and the ground-based Global Oscillation Network Group (GONG).

These instruments have been recording sound waves generated by turbulent plasma motions inside the Sun every 45 to 60 seconds since the mid-1990s. By combining billions of individual measurements, the team assembled one of the longest and most detailed records of the Sun’s internal vibrations ever compiled.

«Helioseismology is still a young field — reliable observations only began in the mid-1990s when GONG first came online,» said Krishnendu Mandal, lead author and NJIT research professor of physics. «Now, with nearly three 11-year solar cycles of data, we’re finally seeing clear patterns that give us a window inside the star.»

The Tachocline: The Engine Room of the Solar Dynamo

Much like seismologists probing Earth’s interior by studying earthquakes, the NJIT team analyzed sound waves rippling through the Sun, measuring shifts in those waves’ travel times through the solar interior. This approach reveals how hot plasma moves and rotates at depth, exposing bands of faster and slower rotation beneath the surface.

The analysis revealed that migrating rotation bands in the deep solar interior form a butterfly-shaped flow pattern — precisely mirroring the sunspot migration that later appears at the surface. Tracing those bands inward led the researchers to a critical transition layer: the tachocline, located roughly 200,000 kilometers down.

The tachocline separates the Sun’s turbulent outer convection zone — where plasma churns and rises — from its stable radiative interior below. Across this boundary, the Sun’s rotation changes abruptly, generating powerful shearing flows capable of powering its magnetic fields.

«Sunspots are the visible footprints of magnetic fields that drive space weather on the Sun’s surface,» Mandal explained, «but what solar oscillation data tells us is that the actual engine room responsible for generating them originates much deeper.»

Direct Observational Evidence for the Solar Dynamo

One of the study’s most significant contributions is establishing a clear observational link between deep interior dynamics and global solar activity. The correlation between flow patterns recorded across all three instruments and the surface sunspot migration pattern provides direct evidence connecting what happens 200,000 kilometers down to what we observe above.

«For years, we suspected the tachocline was important for the solar dynamo, but now we have clear observational evidence,» Mandal said.

Rotation bands originating near the tachocline can take several years to propagate to the surface — a lag that, if properly modeled, could improve long-range forecasts of solar activity. Powerful solar eruptions — flares and coronal mass ejections — can disrupt satellites, communications infrastructure, navigation signals, and power grids on Earth.

«Many current simulations account for processes only in near-surface layers, but our results show the entire convection zone, especially the tachocline, must be considered,» Mandal noted.

Implications Beyond Our Star

The findings carry potential significance well beyond the solar system. Many stars across the galaxy exhibit magnetic cycles similar to the Sun’s, but the high-resolution data achievable for the Sun — owing to its proximity to Earth — is unattainable for any other star. Understanding the solar dynamo therefore provides a theoretical and observational framework for studying magnetic activity in stars throughout the Milky Way.

The team at NJIT’s Center for Computational Heliophysics, co-led by Distinguished Professor Alexander Kosovichev, plans to extend the analysis and refine numerical simulations to deepen understanding of how the dynamo evolves and drives solar activity across multiple cycles.

«There’s still much we don’t know about how the Sun’s internal magnetism evolves,» Mandal acknowledged. «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.»

Source: Krishnendu Mandal et al., Helioseismic evidence that the solar dynamo originates near the tachocline, Scientific Reports (2026). DOI: 10.1038/s41598-025-34336-1

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