pots on Earth's Closest Star] The sun's spots and magnetic field Sunspots are patches on the surface of the sun that can be as large as Earth. The origin of these structures is unknown, but they are caused by intense magnetic activity and sometimes erupt into energetic solar storms that blast streams of charged particles into space. Powerful solar storms can occasionally wreak havoc on Earth's magnetic field by knocking out power grids, disrupting satellites, or posing hazards to astronauts in space. Astronomers keep a close eye on sunspots because their number and frequency act as indicators of the sun's activity, which fluctuates on a roughly 11-year cycle. Typically, the sun takes about 5.5 years to ramp up from a solar minimum, when there are few sunspots, to a solar maximum, when sunspot activity is amplified. [Worst Solar Storms in History] Previously, sunspot regions could only be observed after they appeared on the surface, the researchers said, and little is known about the complex processes in the solar interior that give rise to the dark features. Ilonidis and his colleagues examined sound waves and vibrations generated by the turbulent movement of plasma inside the sun. This technique, called helioseismology, is similar to how scientists study seismic events like earthquakes on Earth. Listening to the sun The astronomers zeroed in on specific regions of the sun and selected pairs of reference points on the solar surface to measure the time it takes for sound waves to travel between the two locations from a depth of about 37,300 miles (60,000 kilometers). "These waves travel along a path inside the solar interior," said Junwei Zhao, one of the study's co-authors. "Travel times get perturbed if there are magnetic fields located along the wave's travel path." Using this time-distance seismology, the researchers found that when acoustic waves crossed a sunspot, they propagated faster, making the travel times shorter. For a large sunspot, the discrepancy was between 12 to 16 seconds, Ilonidis said. "We made a travel-time map that showed which locations inside the sun had longer and shorter travel times," Ilonidis said. "We identified locations where the travel time was significantly shorter, and from that, we could see that this location is a sunspot region." After the astronomers identified these active areas, large emerging sunspot regions became visible on the solar surface one day later, and smaller sunspot regions appeared two days later. The study's findings are published