The Sun’s magnetic field may originate closer to the solar surface

By Will Dunham

WASHINGTON (Reuters) – The Sun’s magnetic field, which causes solar storms like the one that hit Earth this month and produced beautiful auroras, may originate at shallower depths within the star than previously thought, according to researchers.

The outer 30% of the Sun is made up of an “ocean” of churning gases that plunge more than 130,000 miles (210,000 km) below the solar surface. The research, which compares new theoretical models with observations from the Sun-observing SOHO spacecraft, provides strong evidence that its magnetic field is generated near the top of this ocean – less than 5% inland, or about 20,000 miles (32,000 km) – rather than near the bottom, as long as hypothesized.

In addition to providing information about the Sun’s dynamic processes, the findings could improve the ability to predict solar storms and protect against potential damage to electrical grids, radio communications and orbiting satellites, researchers said.

Most stars have magnetic fields, apparently generated by the movement of superheated gases within them. The Sun’s ever-changing magnetic field drives the formation of sunspots – dark, changing spots – on its surface and triggers solar flares that launch hot, charged particles into space.

“The top 5% to 10% of the Sun is a region where the winds are perfect for creating abundant magnetic fields through a fascinating astrophysical process,” said Geoffrey Vasil, an applied and computational mathematician at the University of Edinburgh in Scotland and lead author . of the study published on Wednesday in the journal Nature.

This process involves rotational flow patterns of superheated – electrically charged – ionized gases called plasma within the sun.

The precise mechanisms behind how the Sun generates its magnetic field – the solar dynamo, as scientists call it – remain an unsolved problem in theoretical physics. These researchers hypothesize that these flow patterns are key.

“If the plasma that makes up the Sun were completely stationary, we know that the Sun’s magnetic field would decay over time, and before long there would be no sunspots or other solar activity. However, the plasma in the Sun is moving, and This movement is capable of regenerating and maintaining the Sun’s magnetic field,” said theoretical physicist and study co-author Daniel Lecoanet, from Northwestern University in Illinois.

The solar magnetic field ebbs and flows in a distinct pattern, with sunspots – regions with very large magnetic fields – appearing and disappearing every 11 years, making the Sun, as Vasil called it, “a giant magnetic clock.”

“But we still haven’t figured out the full story about how this happens. Complex motions of interacting fluids (in this case, solar plasma) drive a dynamo, but we can’t yet explain the details,” Vasil added.

The Italian polymath Galileo made the first detailed observations of sunspots in 1612 using telescopes he invented. American astronomer George Hale, in the early 20th century, determined that sunspots were magnetic.

“And we’re still scratching our heads over those pesky sunspots,” Vasil said.

A powerful solar storm that hit Earth this month caused bright auroras in the skies, although Earth’s technological infrastructure remained unscathed.

“Occasionally, a group of sunspots explodes and launches a billion tons of hot charged particles toward Earth, as happened last week,” Vasil said.

But a powerful solar storm like the one that occurred in 1859, called the Carrington Event, could cause trillions of dollars in damage and leave hundreds of millions of people without power, researchers said.

“You can think of magnetic fields as rubber bands. Movements near the surface of the Sun can stretch the rubber bands until they break. The rupture of the magnetic field can then launch material into space, in what is called a solar storm. If we don’t have Luckily, these storms can be launched toward Earth and cause significant damage to our satellites and the electrical grid,” Lecoanet added.

(Reporting by Will Dunham; Editing by Lisa Shumaker)