Staring, Blankly: The solar disk with no sunspot activity (NASA)
As perplexing as it may sound, solar researchers are predicting the sun is about to fall into the doldrums, again.
Despite all the incredible solar flare action we've seen in recent months as our nearest star ramps up toward solar maximum, which is expected to occur in 2013, scientists are predicting the next solar cycle (Cycle 25) will be notable in that it might not even happen.
Remember the deep solar minimum that persisted for the first two years of this solar cycle? Well, it could get worse than that.
This finding was announced today at the 2011 meeting of the Solar Physics Division of the American Astronomical Society, being held at New Mexico State University in Las Cruces.
Researchers from the National Solar Observatory (NSO) and the Air Force Research Laboratory have collected a number of observations of the solar interior, visible surface and corona (the sun's atmosphere), and all the data points to an incredibly lazy sun in the near future.
"This is highly unusual and unexpected," Frank Hill, associate director of the NSO's Solar Synoptic Network, said in a conference press release. "But the fact that three completely different views of the sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation."
This conclusion is based on three separate, but related, fields of solar study.
First, solar astronomers using the Global Oscillation Network Group observing stations — a system that measures pulsations on the solar surface to understand the internal structure of the sun — have not detected the sun's "torsional oscillation."
This east-west flow of plasma inside the sun normally indicates the onset of sunspot formation for the next solar cycle. Before Cycle 24 commenced, the position and strength of the torsional oscillation correctly predicted the late arrival of this cycle's sunspot activity.
But its non-detection points to some rather strange solar behavior. "We expected to see the start of the zonal flow for Cycle 25 by now," said Hill, "but we see no sign of it. This indicates that the start of Cycle 25 may be delayed to 2021 or 2022, or may not happen at all."
The spectacular solar flare of June 8: A thing of the past? (NASA/SDO/AIA)
In another line of research — a study I've been following with great interest for some time — Kitt Peak astronomers Matt Penn and William Livingston have been studying sunspot magnetic field strength data since 1991. Although 20 years is a very short period in solar terms, they've noticed a magnetic weakening trend.
For a sunspot to form on the solar surface, the magnetic field needs to attain a certain strength to push the surface plasma aside, exposing the solar interior as a cool spot — a sunspot.
These magnetic forces are monstrous when compared with the magnetic field strength of our planet — which measures in at less than 1 gauss at the Earth's surface. To maintain a sunspot, the magnetic field threading through the surface needs to be at least 1,500 gauss.
By Penn and Livingston's reckoning, the decline in measured magnetic field strength inside sunspots in recent years points to future sunspots possessing magnetic fields below the 1,500-gauss threshold. This means — you guessed it — sunspots can't exist at all.
When is this magnetic field weakening predicted to dip below the threshold? Only four years from now, in 2015.
In a third line of inquiry, Richard Altrock, manager of the Air Force's coronal research program at NSO's facility in Sunspot, N.M., has noticed a slowdown in the "poleward rush" of magnetic activity in the sun's corona as Cycle 24 has progressed.
Usually, the magnetic field tied into the corona will drift from approximately 70 degrees latitude at the start of each 11-year solar cycle and move poleward, eventually reaching as far as 85 degrees north. However, due to the sluggish nature of the current solar cycle, it is unknown whether this poleward rush will happen at all.
"A key thing to understand is that those wonderful, delicate coronal features are actually powerful, robust magnetic structures rooted in the interior of the sun," said Altrock. "Changes we see in the corona reflect changes deep inside the sun."
All these factors appear to converge on a common conclusion: Something weird is going on inside the sun, and theorists are currently at a loss to explain the phenomenon.
But one thing is for certain — the sun is slowing down and magnetic activity is growing weaker. Could the next solar cycle be the weakest in modern history? Might Cycle 25 not start at all? Are sunspots a thing of the past?
Maunder Minimum 2.0?
Although it might be a mystery, we have possibly experienced this phenomenon before.
Beginning in 1645, astronomers monitoring the sun observed no sunspots for 70 years. This period is known as the "Maunder Minimum," and it is thought to be tied into a long-term cycle where the sun's magnetic activity shuts down.
On Earth the "Little Ice Age" froze Europe around the same time, and a growing body of evidence suggests the sun's slowdown may have caused the climate to cool.
Over the coming months and years, solar physicists will be watching the sun very closely, waiting to see if sunspot activity picks up or shuts down completely. So enjoy the current rash of solar flares and beautiful coronal mass ejections; it might be some time before we see a solar cycle like this again.