Sun storms are powered by a magnetic engine 16 Earths deep, study finds

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The sun’s powerful magnetic dynamo, which powers sunspot activity and helps trigger powerful solar flares and coronal mass ejections, has been confirmed to exist 124,000 miles (200,000 kilometers) below the sun’s visible surface, equivalent to 16 widths of Earth’s depth.

EarthThe magnetic dynamo is located in the outer core of our planet, where the convection of molten iron generates electric currents.

THE sunThe core of is a nuclear furnace of shredded atoms, and its inner two-thirds constitute a radiative zone of gamma rays photons, so the solar magnetic field cannot be generated there. Instead, all convection takes place in the outer third of the sun, in the aptly named convective zone.

Some scientists wondered whether the Sun’s magnetic dynamo was located in a narrow layer near the surface, or whether it perhaps extended across the entire convective layer. The most popular hypothesis, however, is that the magnetic dynamo is generated at the boundary between the lower convective zone and the inner radiative zone.

We call this boundary the tachocline, and after about 30 years of studying oscillations reverberating across the sun’s visible surface – the photosphere – and its deep interior, Krishnendu Mandal and Alexander Kosovichev of the New Jersey Institute of Technology found direct evidence that the dynamo is generated there.

“For years we suspected that tachocline was important to the solar dynamo, but now we have clear observational evidence,” Mandal said in a statement. statement. “[But] until now, we simply haven’t heard enough about the star’s interior to know for sure where the Sun’s intense magnetic fields are organized. »

Mandal and Kosovichev used data collected by the Michelson Doppler imager on the joint NASA-ESA project. Solar and heliospheric observatory (SOHO), launched in 1995, and the National Solar Observatory’s ground-based Global Oscillation Network group, consisting of six telescopes around the world, came online the same year.

SOHO and GONG are still active, and between them they measure the evolution of oscillations that propagate through the photosphere every 45 to 60 seconds.

The oscillations are influenced by the structure of the Sun’s interior, defined by plasma flows within the convective layer. The temperature and motion of these rotational plasma flows therefore affect the period and amplitude of the oscillations as they pass through the flows before passing through the photosphere.

Mandal and Kosovichev discovered that these rotating plasma bands inside the Sun form a butterfly-shaped pattern that matches the object’s location. sunspots changes during the Sun’s 11-year cycle of magnetic activity. Sunspots are cooler areas of the sun created by magnetic fields passing through the photosphere. As such, they constitute a fingerprint of the solar magnetic field.

“Now, with nearly three solar cycles of 11 years of data, we are finally seeing clear patterns emerging that give us a window into the star’s interior,” Mandal said.

Measurements show that this butterfly pattern comes from the tachocline, located 200,000 kilometers below the photosphere’s sunspots. In the tachocline, the plasma rotation is distinct from the convective layer above, with more shear motions driving the electric current generating the magnetic field.

“Rotating bands from magnetic structural changes near the Sun’s tachocline may take several years to propagate to the surface,” Mandal said. “Tracking these internal changes gives us a clear picture of how the solar cycle unfolds.”

Additionally, a better understanding of how the solar magnetic field is generated and how it manifests on the surface in active regions that produce sunspots, flares and finally coronal mass ejectionscould contribute to better risk forecasting space weather. Solar flares can send clouds of charged particles toward us, which can disrupt satellites, communications and energy networks and put astronauts in danger.

“Although our results cannot yet accurately predict future solar cycles, they highlight the importance of including the tachocline in space weather prediction models,” Mandal said. “Many current simulations only consider processes on near-surface layers, but our results show that the entire convection zone, especially the tachocline, needs to be taken into account.”

Further down the line, the results will help us better understand magnetic activity on other stars. Since our Sun is the only star we can observe up close, it is often used as a reference for understanding other stars.

The results are presented in an article published January 12 in Scientific reports.