Scientists have discovered previously unseen solar plasma vortices swirling across the Sun’s surface. These tiny whirlpools could help explain how the Sun stores, transports, and releases magnetic energy—and may offer new insights into solar flares, nanoflares, and the Sun’s 11-year magnetic cycle.
The discovery was made by researchers from the U.S. National Science Foundation National Solar Observatory (NSF NSO), Germany’s Max Planck Institute for Solar System Research (MPS), and the High Altitude Observatory (HAO) in the United States. The team combined observations from the NSF Daniel K. Inouye Solar Telescope—the world’s largest solar telescope—with advanced computer simulations.
Located in Hawaii and built and operated by NSF NSO, the Daniel K. Inouye Solar Telescope captured images detailed enough to reveal previously invisible plasma motions. Researchers also used a broadband imaging camera supplied by the Max Planck Institute for Solar System Research.
“To detect the vortices, we needed to resolve structures on the solar surface about 20 kilometers in size. That is at the limit of what even the world’s largest solar telescope and state-of-the-art simulations can achieve,” said Michiel van Noort, an MPS scientist and co-author of the study. Van Noort contributed to the observations, data reduction, and image restoration.
Solar Plasma Vortices Form Along Granule Boundaries
The newly observed vortices appear along the edges of structures called solar granules, which cover much of the Sun’s visible surface. Individual granules typically measure between 500 and 2,000 kilometers across.
Collectively, these granules create the Sun’s constantly changing granulation pattern, which resembles bubbles in boiling water. The comparison reflects the physical process involved: hot plasma rises from the Sun’s interior, cools near the surface, and then sinks back downward.
For the first time, scientists resolved extremely thin, fringe-like structures along the boundaries of the granules. These structures repeatedly develop swirling motions that resemble ocean waves as they begin to break.
Some of the fringes are only slightly wider than 20 kilometers. Detecting structures this small on the Sun is comparable to seeing a one-euro coin from approximately 180 kilometers away.
Kelvin-Helmholtz Instabilities in the Sun’s Atmosphere
The researchers believe the swirling plasma flows are evidence of Kelvin-Helmholtz instabilities, a well-known phenomenon in fluid dynamics.
Kelvin-Helmholtz instabilities occur when two fluids or layers of fluid move alongside one another at different speeds. This velocity difference creates shear forces at the boundary between them. Small disturbances along that boundary can grow into waves and eventually form rotating vortices.
The same process occurs in many environments and at vastly different scales, including on lake surfaces, in ocean waves, during cloud formation, in the atmospheres of Jupiter and Saturn, and where the solar wind interacts with planetary magnetospheres.
At the boundaries of solar granules, neighboring layers of plasma also appear to move at different speeds. These conditions may create the shear needed for Kelvin-Helmholtz instabilities to develop on the Sun’s surface.
How Tiny Solar Vortices May Twist Magnetic Fields
The discovery of solar plasma vortices could help scientists understand how the Sun stores and releases energy in its magnetic field. This process may include tiny bursts of radiation known as nanoflares.
According to current theories, magnetic energy accumulates as the Sun’s magnetic field lines twist and coil—much like the energy stored in a tightly wound metal spring. As the twisting intensifies, the magnetic field becomes increasingly energetic and unstable.
That stored energy can eventually be released through a process called magnetic reconnection. During reconnection, magnetic field lines break apart and reconnect in a new configuration, releasing energy in the process.
However, scientists have long questioned what initially twists the Sun’s magnetic field lines.
The newly detected vortices could provide part of the answer. The researchers found that these small whirlpools appear continuously in regions where the magnetic field is strong enough. As a result, the vortices may provide an ongoing mechanism for twisting magnetic field lines across the solar surface.
New Clues About the Sun’s 11-Year Magnetic Cycle
The analysis also suggests that the mini-vortices efficiently mix magnetized and non-magnetized plasma near the Sun’s surface. This process could help transport magnetic fields rapidly upward into the solar atmosphere.
Changes in the Sun’s magnetic field drive its approximately 11-year activity cycle, a remarkably fast transformation on cosmic timescales. For the Sun’s magnetic structure to change so quickly, magnetic flux must be transported efficiently away from the surface and through the atmosphere.
Existing solar models have struggled to explain how this magnetic diffusion occurs at such a rapid rate. The newly identified plasma vortices could provide an important piece of the puzzle.
“The newly discovered plasma vortices impressively demonstrate how minute processes—at the limit of what we can resolve using all available techniques—significantly determine the nature of our star,” said Sami K. Solanki, director of the Max Planck Institute for Solar System Research and a co-author of the study.
Source: www.sciencedaily.com