Carlos Solis
In 2019, at the end of the previous solar cycle, Cycle 24, researchers predicted that the next cycle would be just as mild as the last.
However, that prediction turned out to be incorrect. The current Cycle 25, which will last until 2030, has proven to be much more intense than expected by NASA and NOAA. Scientists now say solar activity is increasing beyond the typical 11-year cycle. A new analysis of data shows that solar activity has been gradually rising since 2008.
NASA (the National Aeronautics and Space Administration) and NOAA (the National Oceanic and Atmospheric Administration) are both U.S. agencies.
“All signs indicated that the Sun was entering a prolonged phase of low activity. So it was a surprise for us that this trend has changed. The Sun is slowly waking up,” said Jamie Yasinetsky, a plasma physicist at NASA’s Jet Propulsion Laboratory (JPL).
The Sun — a complex and unpredictable machine
Our star looks steady, but its life is turbulent and changeable. Approximately every 11 years, solar activity reaches a peak before falling back to a minimum, as reported by Science Alert.
This activity shows up as a big increase in sunspots, flares, coronal mass ejections, and shifts in the Sun’s magnetic polarity.
According to historical observations, we are currently in the 25th solar cycle, which means scientists have been tracking the Sun’s behavior for centuries, using sunspots as an indirect indicator of activity. Yet despite the large amount of data, predicting these cycles remains an imprecise art. Many more processes inside the Sun drive these changes, and scientists are still trying to explain them.
For instance, during the 70-year period from 1645 to 1715, there were virtually no sunspots. This period is known as the Maunder Minimum. A similar lull was observed between 1790 and 1830 (the Dalton Minimum).
“In reality, it is unknown why the Sun experienced a 40-year minimum that began in 1790. Long-term trends are much less predictable, and we do not yet fully understand them,” Yasinetsky said.
The recent 22nd and 23rd solar cycles were fairly average in sunspot activity. Nevertheless, the pressure of the solar wind steadily decreased throughout both cycles. That decline led scientists to speculate we might be heading toward something like the Maunder or Dalton minima.
In 2008, the 24th solar cycle began, and it became one of the weakest cycles in recorded history for sunspot and flare activity. Researchers assumed the 25th cycle would be similar; however, its activity level has turned out to be above average.
Yasinetsky and his colleague, space physicist Marco Velli from NASA’s Jet Propulsion Laboratory, analyzed long-term solar activity data and discovered something remarkable. In 2008, at the start of the 24th solar cycle, the strength of the solar wind began to steadily increase. This trend continues to this day.
The strength of the solar wind is measured by its speed, density, temperature, thermal pressure, mass, momentum, energy, and magnetic field strength. Each of these parameters has increased.
The Sun is extraordinarily complex. Predicting its future behavior is extremely challenging. Yasinetsky and Velli say their findings point to a possible increase in disruptive space weather, characterized by stronger solar wind, solar storms, flares, and coronal mass ejections.
The results were published in The Astrophysical Journal Letters.
Photo: pixabay.com
