Polar vortices exist in the atmospheres of planets ranging from rocky Earth-like planets to gas giants like Jupiter and Saturn. However, currently not much is known about their presence and characteristics on the Sun due to the lack of direct observations in the polar regions. Unlike planetary atmospheres, the Sun’s underground layers are greatly influenced by the presence of magnetic fields. New research shows that the solar cycle’s magnetic fields provide the mechanism for the formation of polar vortices in the Sun.
On August 31, 2012, the corona, a long filament of solar material suspended in the Sun’s atmosphere, erupted into space at 4:36 p.m. EDT. CME traveled at more than 900 miles per second. Although it did not fly directly towards Earth, the single shot connected with Earth’s magnetic environment, or magnetosphere, and caused the aurora borealis to appear on the night of September 3rd. Image credit: NASA’s Goddard Space Flight Center.
“No one can say exactly what’s going on at the solar pole,” says Dr. Mausmi Dikpati, a senior scientist at the NSF National Center for Atmospheric Research’s High Altitude Observatory.
“But this new study gives us an interesting look at what we might expect to find when we are able to observe the solar pole for the first time.”
It is not surprising that some kind of polar vortex may exist on the Sun.
These rotating geological formations develop in the fluid surrounding rotating bodies due to the Coriolis force and are observed on most planets in the solar system.
On Earth, vortices rotate high in the atmosphere around both the north and south poles.
When these vortices are stable, frigid air is trapped at the poles, but when they weaken and become unstable, that cold air penetrates toward the equator, creating cold air in the midlatitudes. cause
NASA’s Juno mission has returned breathtaking images of Jupiter’s polar vortices, showing there are eight tightly packed vortices around the gas giant’s north pole and five around its south pole.
Saturn’s polar vortex, observed by NASA’s Cassini spacecraft, is hexagonal at the north pole and more circular at the south pole.
These differences provide scientists with clues to the composition and dynamics of each planet’s atmosphere.
Polar vortices have also been observed on Mars, Venus, Uranus, Neptune, and Saturn’s moon Titan, so the fact that the Sun (also a rotating body surrounded by fluid) has such a feature may be obvious in some ways. yeah.
However, the sun is fundamentally different from planets and satellites, which have atmospheres. The plasma surrounding the sun is magnetic.
How that magnetism affects the formation and evolution of the Sun’s polar vortex, or whether it forms at all, remains a mystery. This is because humans have never sent a probe into space that can observe the poles of the sun.
In fact, our observations of the Sun are limited to views of the Sun’s face when it points towards the Earth, which only provides hints about what’s happening at the poles.
Astronomers have never observed the sun’s poles, so the study authors turned to computer models to fill in the blanks about what the sun’s polar vortex looks like.
What they discovered is that the Sun does indeed likely have a unique polar vortex pattern that evolves as the solar cycle unfolds and depends on the strength of the particular cycle.
Simulations show that a tight ring of polar vortices forms at about 55 degrees latitude, which corresponds to Earth’s Arctic Circle, at the same time that a phenomenon called “polar plunge” begins.
At the maximum of each solar cycle, the magnetic field at the sun’s poles disappears and is replaced by a magnetic field of the opposite polarity.
This flip-flop is preceded by a “polar plunge” in which a magnetic field of opposite polarity begins to move toward the pole from about 55 degrees latitude.
After formation, the vortices move towards the poles within the constricting ring, releasing the vortices as the circle closes, until eventually only a pair of vortices directly adjacent to the poles remain, completely disappearing during solar maximum.
The number of vortices that form and their configuration as they move toward the poles changes with the strength of the solar cycle.
These simulations provide a missing piece to the puzzle of how the Sun’s magnetic field behaves near the poles and could help answer some fundamental questions about the Sun’s solar cycle.
For example, many scientists have traditionally used the strength of the magnetic field “pushing to the poles” as a proxy for how strong future solar cycles are likely to be.
However, the mechanism of how they are connected, if at all, is not clear.
The simulation also provides information that can be used to plan future missions to observe the Sun.
In other words, this result shows that some form of polar vortex is observable during all parts of the solar cycle except during solar maximum.
“You could launch a solar mission and arrive at the pole at exactly the wrong time,” says Scott McIntosh, also of the NSF National Center for Atmospheric Research’s High Altitude Observatory.
Solar Orbiter, a joint mission between NASA and ESA, may give researchers their first glimpse of the solar pole, but the first glimpse will be close to solar maximum.
Scientists say a mission aimed at observing the poles and providing researchers with multiple simultaneous views of the sun could help solve long-standing questions about the sun’s magnetic field.
Dr. McIntosh said, “Our conceptual boundaries are that we currently operate from only one perspective.”
“To make significant progress, we need the necessary observations to test our hypotheses and see if simulations like this are correct.”
of result will appear in Proceedings of the National Academy of Sciences.
_____
Mausumi Dikpati others. 2024. Magnetohydrodynamic mechanism of solar polar vortex formation. PNAS 121 (47): e2415157121;doi: 10.1073/pnas.2415157121
