Scientists use an prolonged, 22-year solar cycle to make the forecast — ScienceDaily
In direct contradiction to the official forecast, a team of scientists led by the National Center for Atmospheric Research (NCAR) predicts that the sunspot cycle that began this fall could be one of the strongest on record.
In a new article published in Solar Physics, the research team predicts that sunspot cycle 25 will peak with a maximum sunspot number between approximately 210 and 260, which would bring the new cycle into the society of the few top cycles ever observed .
The cycle that has just ended, Sunspot Cycle 24, peaked with a sunspot number of 116, and the consensus forecast of an expert panel convened by the National Aeronautics and Space Administration (NASA) and the National Ocean and Atmosphere Administration (NOAA) , Sunspot Cycle 25 is predicted to be similarly weak. The panel predicts a maximum sunspot number of 115.
If confirmed, the new NCAR-driven forecast would support the research team’s unorthodox theory – detailed in a number of papers published over the past decade – that the Sun has 22-year overlapping magnetic cycles that interact to produce the well-known, approximately 11-year sunspot cycle as a by-product. The 22-year cycles repeat themselves like clockwork and, according to the authors of the study, could be a key to finally making accurate predictions about the time and type of sunspot cycles and many of the effects they cause.
“Scientists have struggled to predict both the length and strength of sunspot cycles because we lack a basic understanding of the mechanism that drives the cycle,” said Scott McIntosh, NCAR associate director, a solar physicist who led the study. “If our prediction proves correct, we will have evidence that our framework for understanding the Sun’s internal magnet machine is on the right track.
The new research was supported by the National Science Foundation, the sponsor of NCAR, and NASA’s Living With a Star program.
Sunspot Cycle 25 starts with a bang. what will follow
In McIntosh’s earlier work, he and his colleagues outlined the outline of a 22 year extended solar cycle using observations of coronal bright spots, short-lived flickering of extreme ultraviolet light in the solar atmosphere. These bright points march from the high latitudes of the Sun to the equator for about 20 years. As they cross the mid-latitudes, the bright spots coincide with the appearance of sunspot activity.
McIntosh believes that the bright spots mark the movement of magnetic field ribbons that wrap around the sun. When the bands of the northern and southern hemispheres – which have oppositely charged magnetic fields – meet at the equator, they annihilate each other, resulting in a “terminator” event. According to McIntosh, these terminators are important markers for the 22-year clock of the sun as they mark the end of a magnetic cycle along with the corresponding sunspot cycle and act as a trigger for the start of the following magnetic cycle.
While one set of oppositely charged ribbons is about the middle of its migration to the equatorial meeting, a second set appears at high latitudes and begins its own migration. While these bands occur at a relatively constant rate at high latitudes – every 11 years – they sometimes slow down as they cross mid-latitudes, which seems to weaken the strength of the upcoming solar cycle.
This happens because the slowdown increases the amount of time the oppositely charged sets of bands within the sun overlap and interfere with each other. The slowdown extends the current solar cycle by postponing the terminator event in time. If you slide out the terminator in a timely manner, it will affect the productivity of the next cycle on site.
“If we look back on 270 years of observational record of terminator events, we see that the longer the time between terminators, the weaker the next cycle,” said study co-author Bob Leamon, a researcher at the university of Maryland Baltimore District. “Conversely, the shorter the time between the terminators, the stronger the next solar cycle.
This correlation has been difficult for scientists to see in the past because they have traditionally measured the length of a sunspot cycle from solar minimum to solar minimum, which is defined in terms of an average rather than an accurate event. In the new study, the researchers measured from terminator to terminator, which allows for much greater precision.
While terminator events occur roughly every 11 years and mark the beginning and the end of the sunspot cycle, the time between terminators can vary by years. For example, Sunspot Cycle 4 started with a terminator in 1786 and ended with a terminator in 1801, an unprecedented 15 years later. The following cycle, 5, was incredibly weak, with a peak amplitude of only 82 sunspots. This cycle would become known as the start of the “Dalton” Grand Minimum.
Similarly, Sunspot Cycle 23 began in 1998 and didn’t end until 2011, 13 years later. Sunspot Cycle 24, which is just ending, was also quite weak, but also quite short – just under 10 years – and that is the basis for the new study’s optimistic prediction that Sunspot Cycle 25 will be strong.
“Once you identify the terminators on the historical record, the pattern becomes apparent,” McIntosh said. “A weak Sunspot cycle 25, as the community predicts, would be a complete departure from everything the data has shown us up to that point.