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Tracking Dynamo Waves Inside the Sun to Fathom the Solar Cycle

This visualization shows zones of plasma flow acceleration (red) and deceleration (blue) beneath the Sun’s surface. The bottom of the convection zone, or tachocline (A), is the primary seat of the solar dynamo, where the magnetic field originates. Tracking the flow acceleration allows scientists to infer the motion of the magnetic field, and reveals that the field splits into two branches: the polar branch (C), and the equatorial branch (B), where the maximum magnetic strength leads to the formation of sunspots. Alexander Kosovichev, New Jersey Institute of Technology, Tim Sandstrom, NASA Ames

Deep inside the Sun, dynamic flows of plasma drive magnetic fields through regions starting at the convection zone up through the solar surface, where the magnetic flux appear as dark sunspots. The visualization shown above opens a window into the Sun’s interior workings, revealing evolving dynamo wave patterns that help us understand the solar cycle better than ever before.

The solar dynamo is a process that generates the Sun’s magnetic field, driven by rotating and convective motions that transport energy inside the Sun.

For the first time, scientists have verified that precise measurements of the speed of flows on the solar surface—taken over a 22-year period by two NASA space missions—enable us to detect the start of a new solar cycle long before it travels more than 200,000 kilometers (120,000 miles) from the convection zone to reach the surface. Each cycle culminates every 11 years in the “solar maximum,” when the peak number of sunspots occurs, sometimes accompanied by massive solar flares or coronal mass ejections. These space weather events can disable satellites, disrupt technologies on Earth, cause minor to major power outages, and can harm astronauts aboard the International Space Station and other space missions.

Research scientist Alexander Kosovichev, a member of the NASA's Heliophysics Modeling and Simulation team and professor at the New Jersey Institute of Technology, merged observations from NASA’s Solar and Heliospheric Observatory (SOHO, 1996–2010) and the Solar Dynamics Observatory (SDO, 2010–present) to obtain patterns for two full solar sunspot cycles (Cycle 23 and the current Cycle 24).

By combining the final SOHO and SDO data analysis, run on the agency's Pleiades supercomputer, with images and movies produced by visualization experts in the NASA Advanced Supercomputing Division, Kosovichev was able to pin down the exact location where the solar activity cycles originate in the convection zone. Further, he found that a signal in the solar interior showed a decrease of the zonal acceleration in the current cycle, indicating a decline of sunspot activity in the upcoming cycle (Cycle 25), projected to begin in late 2019.

The ability to predict the strength and timing of the next solar activity maximum will allow organizations around the globe to prepare for and protect our planet and space explorers from future space weather events. As scientists continue monitoring the evolution of subsurface flows on the Sun, will Kosovichev's expectations about the next solar cycle prove correct? For now, we’ll have to wait and see.

—Jill Dunbar, NASA/Ames Research Center

A paper detailing results of research by Kosovichev and colleague Valery Pipin, Institute of Solar-Terrestrial Physics, Russian Academy of Sciences was summarized in a press event at the centennial AGU Fall Meeting, held December 10–14, 2018 in Washington, D.C. (See sidebar)