Model simulations provide insights into the fundamental properties of the Sun's genetic field
The Sun, like Earth, probably has swirling polar vortices, according to new research. But unlike the Earth's atmospheric eddies, the formation and development of these polar eddies is determined by magnetic fields.
The research has important implications for our understanding of the magnetic behavior of the Sun and the solar cycle. This insight could improve our ability to predict weather events in space, which sometimes disrupt systems on the ground. The findings also hold clues about what future missions might observe at the Sun's poles, which will help plan the timing and goals of those missions.
"No one can say for sure what is happening at the poles of the Sun," said senior scientist Maosumi Dikpeti, who led the new study. "But this new study gives us an intriguing look at what we can expect to find when we can, for the first time, observe the Sun's poles."
In this simulation, a tight ring of polar vortices forms at about 55 degrees latitude, which corresponds to the Earth's Arctic Circle. Once formed, the eddies move poleward in a tightening ring, shedding eddies as the circuit closes, and finally only two eddies remain directly bordering the poles before disappearing altogether at solar maximum. The number of eddies that form and their configuration as they move poleward vary with the strength of the solar cycle.
Credit: UCAR
The possible existence of polar vortices of some kind in the Sun is not surprising. These swirling formations develop in fluids surrounding a rotating body due to the Coriolis force, and have been observed on most planets in our solar system. On Earth, a vortex swirls high in the atmosphere around both the North and South Poles. When these eddies are stable, they trap cold air at the poles, but when they weaken and become unstable, they allow this cold air to leak equatorward, causing cold air bursts in the mid-latitudes.
How magnetism might affect the formation and development of polar vortices in the Sun - or whether they form at all - is a mystery because humanity has never sent a mission into space that can observe the Sun's poles. In fact, our observations of the Sun are limited to looking at the surface of the Sun as it faces Earth and provide only hints of what is happening at the poles.
Since we had never observed the Sun's poles, the researchers relied on computer models to fill in the blanks about what polar vortices look like on the Sun. They found that the Sun probably has a unique pattern of polar vortices that develop as the solar cycle progresses and depend on the strength of the particular cycle.
In the simulations, a tight ring of polar vortices forms at 55 degrees latitude at about the same time that a phenomenon called "polar panic" begins. At solar maximum, the magnetic field at the Sun's poles disappears and is replaced by a magnetic field of opposite polarity. This inversion is preceded by a "panic to the poles" when the opposite polarity field begins to move from about 55 degrees latitude to the pole. Such visualization is shown in the video above.
These simulations add a missing piece to the mystery of the behavior of the Sun's magnetic field near the poles and may help answer some fundamental questions about solar cycles.
More of the topic in Hayadan:
