Something strange is happening with the Sun.
So far, nearly every day in 2022 it has erupted in flares and coronal mass ejections, some of which were the most powerful explosions our star has been capable of.
In itself, an erupting Sun is not strange. It erupts regularly during periods of high and low activity in cycles lasting about 11 years.
Current activity is significantly higher than official NASA and NOAA predictions for the current solar cycle, and solar activity has consistently exceeded predictions as of September 2020. But a solar scientist will tell you it’s not all that weird.
“We cannot reliably predict solar cycles,” solar astrophysicist Michael Wheatland of the University of Sydney, Australia, told ScienceAlert.
“We do not fully understand the solar dynamo, which generates the magnetic fields observed on the surface as sunspots, and which generate flares. This is one of the outstanding problems in astrophysics; the inaccuracy in prediction is surprising.” Is.”
Amazing, sure. But what if this lack of wonder – that we expect to be bad at predicting solar cycles – means we need to completely rethink how we do it? What if we’re basing our predictions on the wrong metric?
11 to 22 years
Solar cycles have a huge impact on the solar system but are relatively little understood. Scientists have discovered that they are inextricably linked to the solar magnetic field, which spins in twists, turns and loops across our Sun’s surface.
Roughly every 11 years, the Sun’s magnetic poles reverse, north turns south and vice versa. This switch is known as the solar maximum, which is characterized by the peak of sunspot, flare, and coronal mass ejection (CME) activity.
Image of the Sun from October 2014 showing how sunspots appear in the band. (NASA/SDO)
After this reversal, activity subsides before heading towards the peak once again. This is where we are now – the growth phase of the current cycle, the 25th since we started counting.
Activity cycles are characterized and predicted based on one metric: the number of sunspots observed on the Sun. These are temporary regions where magnetic fields are particularly strong, facilitating the eruption of flares and CMEs. They appear as dark spots because the magnetic field blocks the flow of hot plasma, and the regions subsequently become cooler and dimmer than their surroundings.
According to Scott McIntosh, a solar physicist at the US National Center for Atmospheric Research, predicting solar cycles based on how many sunspots we count is a problem.
“The sunspot cycle isn’t a primary thing. It’s a secondary thing,” he told ScienceAlert. “And the way canon is written, the way textbooks are written, the way solar activity is presented is portrayed as elementary.
“The problem is that it really isn’t, and the underlying Hale cycle, the 22-year magnetic cycle, is primary. And the sunspot cycle is just a small subset of this bigger picture.”
The Hale cycle was discovered by the American astronomer George Ellery Hale in the early 20th century. It consists of two 11-year sunspot cycles – the time it takes for the poles to swap twice, to return to their original position.
Hel cycles, in contrast to 11-year cycles, are observed in many events. These are the changing magnetic polarities of both sunspots and the solar magnetic poles, as well as the intensity of galactic cosmic rays on Earth.
Solar activity makes it difficult for cosmic rays to reach Earth, but odd and even-numbered solar cycles have different cosmic radiation waves. This has been attributed to the polarity of the solar magnetic field.
Sunspot Explanation
It’s important to understand that we don’t really have a good idea of what happens. within Sun. The solar magnetic field is thought to be generated inside the star by a dynamo, a rotating, convection and electrically conductive fluid that converts kinetic energy into magnetic energy, propelling a magnetic field into space around the Sun. .
If so, what caused the sunspots? Well, according to current models, they are related to the rotation of the Sun. The solar equator rotates faster than the poles. If longitudinally running straight magnetic field lines are drawn along this rotation, they are stretched and eventually entangled, producing temporary, localized regions of strong magnetic fields or sunspots.
According to Macintosh, it is based on the deactivation of the magnetic field.
“You have a very complex system inside the Sun. Like all physical systems, we make simplifications or guesses to try and understand what’s going on,” he explained.
“About 60 years ago, they conjectured — along with the magnetic fields — that they were smaller than the fluids on the Sun. So, when the Sun is rotating, like our planet does, the rotational circulation heats the atmosphere. operates, and with all this movement going on, the magnetic fields just get dragged along with the circulation.”
Animations that show this effect align very well with observational data for sunspots, with the initial magnetic field visible at about 30 degrees latitude. But, according to Mackintosh and his colleagues, that’s because the model was designed to explain exactly that and only that.
And there is an alternative explanation: the sunspot is an interference pattern, generated by the magnetic fields of the overlapping Hale cycles.
McIntosh and his colleagues first noticed a pattern emerging in sunspot data in 2011, called a butterfly diagram. These are graphs that plot sunspot appearances based on latitude over time.
Animation showing how oppositely polarized waves, appearing as sunspots, terminate at the equator when a new wave appears. (Scott McIntosh/NCAR)
Once they saw it, the researchers looked for more and more historical sunspot data and traced them back to the 1860s.
They found that this overlap continued to appear. At the end of one sunspot cycle, as sunspots appear closer and closer to the equator, the appearance of the next cycle’s sunspots can be seen at mid-latitudes.
These indicators are, the researchers found, oppositely polarized bands of magnetic activity that make their way across the Sun in cycles; They would be responsible for the sunspot cycle, but would not be inspired by it. In addition, chakras can interact; When two circles of opposite polarity overlap, they interfere with each other.
The result is that the magnetic systems mutually inhibit the production of sunspots, and a period of minimal sunspot activity ensues.
“The sunspot cycle is the result of an interaction between these larger magnetic cycles,” Mackintosh told ScienceAlert. “In other words, it’s like an interference pattern. Magnetic fields want to cancel each other out all the time.”
More data, always more data
Based on the findings of the ‘interference pattern’, Mackintosh and his team have arrived at predictions of the current solar cycle that are more consistent with current observations than official predictions – which are based on sunspot calculations.
However, at this stage it is all theoretical.
We still don’t know, for example, what drives the bands of magnetic activity in the Sun; Researchers think it may be gravitational waves, but we don’t have enough information to be able to tell at this point.
“Scott McIntosh’s ideas are interesting, and Mackintosh/Lemon [that’s Robert Leamon of the University of Maryland’s Goddard Planetary Heliophysics Institute] The forecast for cycle 25 is closer than the official forecast at this stage. However, it is not based on a physical model. I suspect it has more predictive power than other observation-based approaches to prediction,” Wheatland told ScienceAlert.
To know more, we will need more data, which will take time to get. According to Mackintosh, this means viewing the Sun’s high latitudes as a new circle, near the poles.
We don’t usually see the solar poles, because the position of the Earth orbits the solar equator; But the European Space Agency’s Solar Orbiter will be swooning in just in time for a new cycle to begin.
McIntosh believes his team’s prediction is closer to the fact that solar cycle 25 is going. At the very least, the team’s ideas are worth a closer look and some serious investigation.
“We’ve been pretty spot on for about 10 years, but it hasn’t been spreading through the scientific community,” he said.
“This solar cycle provided an opportunity. Because our prediction was the exact opposite of what the consensus panel was showing, it means that if we get closer, we really need to look at how the stars magnetic field.” make.
“Maybe it’s closer to the way we see it happening, the old way. And it could be a hybrid, some mix of the two. It probably is.”
His team’s most recent paper on solar cycles is published in Frontiers in Astronomy and Space Science,
