Old Solar Cycle Returns

March 28, 2008
Old Solar Cycle Returns
Sunspot counts vs. year: 2008 is a low point in the solar cycle. Smoothed curves are predictions of future activity.

Solar Cycle 23, how can we miss you if you won't go away? Barely three months after forecasters announced the beginning of new Solar Cycle 24, old Solar Cycle 23 has returned. Actually, it never left. Read on.

"This week, three big sunspots appeared and they are all old cycle spots," says NASA solar physicist David Hathaway. "We know this because of their magnetic polarity."

Earlier today, the Solar and Heliospheric Observatory (SOHO) made a magnetic map of the sun.

It shows the north and south magnetic poles of the three sunspots. All are oriented according to the patterns of Solar Cycle 23. Cycle 24 spots would be reversed.

What's going on? Hathaway explains: "We have two solar cycles in progress at the same time. Solar Cycle 24 has begun (the first new-cycle spot appeared in January 2008), but Solar Cycle 23 has not ended."

Strange as it sounds, this is perfectly normal. Around the time of solar minimum--i.e., now--old-cycle spots and new-cycle spots frequently intermingle. Eventually Cycle 23 will fade to zero, giving way in full to Solar Cycle 24, but not yet.

Meanwhile, on March 25th, sunspot 989, the smallest of the three sunspots, unleashed an M2-class solar flare. Flares are measured on a "Richter scale" ranging from A-class (puny) to X-class (powerful). M-class flares are of medium intensity. This one hurled a coronal mass ejection or "CME" into space, but the billion-ton cloud missed Earth.

While the CME was still plowing through the sun's atmosphere, amateur radio astronomer Thomas Ashcraft heard "a heaving sound" coming from the loudspeaker of his 21 MHz shortwave receiver in New Mexico: listen. It was a Type II solar radio burst generated by shock waves at the leading edge of the CME. A thousand miles away in Virginia, David Thomas recorded the same emissions on a chart recorder he connected to his 20 MHz ham rig. "What a pleasant surprise," says Thomas.

We could get more of this kind of activity in the next 7 to 10 days. It will take about that long for the sunspots to cross the face of the sun. The sun's rotation is turning the spots toward Earth, which means the next CME, if there is one, might not miss. CME strikes do no physical harm to Earth but they can cause Northern Lights, satellite glitches and, in extreme cases, power outages.

The real significance of these spots is what they say about the solar cycle, says Hathaway. "Solar Cycle 24 has begun, but we won't be through solar minimum until the number of Cycle 24 spots rises above the declining number of Cycle 23 spots." Based on this latest spate of "old" activity, he thinks the next Solar Max probably won't arrive until 2012.

Source: by Dr. Tony Phillips, Science@NASA

Explore further: Scientists test world's first solar fuels reactor for night

Related Stories

Scientists test world's first solar fuels reactor for night

February 21, 2018

International solar thermal energy researchers have successfully tested CONTISOL, a solar reactor that runs on air, able to make any solar fuel like hydrogen and to run day or night - because it uses concentrated solar power ...

Image: 22 years of SOHO

February 26, 2018

The activity cycle of the sun – where the number of sunspots increase and decrease – has been monitored regularly for around 250 years, but the use of space-based telescopes has given us a whole new perspective of our ...

Team proposes new space-weather forecasting method

December 18, 2017

Scientists from Skoltech, the University of Graz and the Royal Observatory of Belgium have developed a method to forecast the strength of the 11-year solar activity cycle. The results of this study may shed light into the ...

Recommended for you

NASA powers on new instrument staring at the Sun

March 16, 2018

NASA has powered on its latest space payload to continue long-term measurements of the Sun's incoming energy. Total and Spectral solar Irradiance Sensor (TSIS-1), installed on the International Space Station, became fully ...

Dawn reveals recent changes in Ceres' surface

March 15, 2018

Observations of Ceres have detected recent variations in its surface, revealing that the only dwarf planet in the inner solar system is a dynamic body that continues to evolve and change.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.