Recent research suggests that, similar to Earth, the Sun may also have swirling polar vortices. However, the development and evolution of these vortices on the Sun are influenced by magnetic fields, which sets them apart from those on Earth.
These important findings, which have been detailed in the Proceedings of the National Academy of Sciences (PNAS), enhance our understanding of the Sun’s magnetism and solar cycles. This knowledge could aid in better predicting disruptive space weather. Furthermore, the study provides insights into what could be observed at the Sun’s poles during upcoming missions and aids in planning when those missions should occur.
“While we can’t be entirely certain about the activities at the solar poles,” remarked Mausumi Dikpati, a senior scientist at NSF NCAR and the study’s lead researcher, “this discovery gives us an exciting preview of what we could see when we finally get to observe the solar poles.”
The research received funding from NSF and NASA, supported by supercomputing resources on NSF NCAR’s Cheyenne and Derecho systems.
The Enigma of Solar Polar Vortices
The potential existence of polar vortices on the Sun is not particularly surprising. These rotating formations are typically formed in fluids around a spinning entity due to the Coriolis effect, and they have been detected on most planets within our solar system. On Earth, vortex formations exist at both the north and south poles within the atmosphere. When these vortices remain stable, they trap cold air at the poles; however, when they weaken, they allow cold air to drift towards the equator, leading to chilly outbreaks in the mid-latitudes.
NASA’s Juno mission provided impressive images of polar vortices surrounding Jupiter, showing eight swirls at the north pole and five at the south. Observations from NASA’s Cassini spacecraft revealed that Saturn’s polar vortices are hexagonal in the north and circular in the south. These variations help scientists learn more about the structure and dynamics of each planet’s atmosphere.
Vortices have also been recorded on Mars, Venus, Uranus, Neptune, and Titan, Saturn’s moon. Thus, it seems reasonable that the Sun, being another rotating object surrounded by a fluid-like environment, could showcase similar features. However, the Sun is distinct from the planets and moons with atmospheres because the fluid surrounding it is composed of plasma that is magnetic in nature.
Determining how this magnetic field may affect the development and transformation of solar polar vortices, or if they even exist, remains a conundrum. Humanity has not yet successfully deployed a mission capable of observing the Sun’s poles. Current observations are confined to the side of the Sun visible from Earth, providing only limited insights into possible activities occurring at the poles.
A Network of Vortices Associated with the Solar Cycle
Given the lack of direct observations of the solar poles, the science team utilized computer models to theorize what solar polar vortices could look like. Their results indicate that the Sun likely possesses a distinctive pattern of polar vortices that changes as the solar cycle progresses and varies based on the cycle’s intensity.
In their simulations, a compact ring of polar vortices emerges around 55 degrees latitude—similar to the Arctic Circle—simultaneously with a phenomenon known as the “rush to the poles.” At the peak of each solar cycle, the magnetic field at the poles vanishes and is replaced by a field of opposite polarity. This transition is preceded by the aforementioned “rush to the poles,” where the opposing magnetic field starts shifting from around 55 degrees latitude toward the poles.
Once formed, the vortices travel toward the poles, creating a tighter ring and shedding excess vortices as the formation consolidates, ultimately leaving only two vortices adjacent to the poles before they completely vanish at solar maximum. The number and arrangement of these vortices as they approach the poles fluctuate based on the solar cycle’s power.
These simulations provide crucial insights regarding the behavior of the Sun’s magnetic field near the poles and may assist in addressing essential inquiries about the Sun’s solar cycles. Historically, scientists have relied on the strength of the magnetic field that “rushes to the poles” as a predictor for the potential intensity of subsequent solar cycles. However, the connection between these phenomena remains ambiguous.
The simulations also furnish information that could guide planning for future observational missions aimed at the Sun. Notably, they suggest that some form of polar vortices should be detectable during various phases of the solar cycle, except during the solar maximum phase.
“It’s possible to launch a solar mission, but it might arrive at a time when observations would be unproductive,” said Scott McIntosh, vice president of space operations for Lynker and co-author of the study.
The Solar Orbiter, a joint mission from NASA and the European Space Agency, may provide scientists with their first look at the solar poles, but this initial view will occur close to solar maximum. The authors stress that a mission dedicated to observing the poles and providing researchers with multiple, simultaneous views of the Sun could significantly advance our understanding of the Sun’s magnetic fields.
“Currently, we are limited to just one perspective,” said McIntosh. “To make real progress, we need comprehensive observations to validate our hypotheses and ascertain whether these simulations hold true.”
