Old Solar Cycle Returns

Mar 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: NASA moisture satellite launch scrubbed due to winds

add to favorites email to friend print save as pdf

Related Stories

What other worlds have we landed on?

Jan 14, 2015

Think of all the different horizons humans have viewed on other worlds. The dust-filled skies of Mars. The Moon's inky darkness. Titan's orange haze. These are just a small subset of the worlds that humans ...

Sun sizzles in high-energy X-rays

Dec 23, 2014

For the first time, a mission designed to set its eyes on black holes and other objects far from our solar system has turned its gaze back closer to home, capturing images of our sun. NASA's Nuclear Spectroscopic ...

ICON cleared for next development phase

Nov 13, 2014

NASA has officially confirmed the Ionospheric Connection Explorer, or ICON, mission, clearing it to move forward into the development phase. ICON will explore a swath of Earth's atmosphere where weather close ...

Life can survive on much less water than you might think

Nov 04, 2014

"Follow the water" has long been the mantra of our scientific search for alien life in the Solar System and beyond. We continue seeking conditions where water can remain liquid either on a world's surface ...

Recommended for you

Scientists launch CubeSats into radiation belts

51 minutes ago

Twin, pintsized satellites built in part at the University of New Hampshire's Space Science Center will be launched into orbit from Vandenberg Air Force Base in California at 9:20 a.m. (EST) Thursday, January ...

Cassini catches Titan naked in the solar wind

51 minutes ago

(Phys.org)—Researchers studying data from NASA's Cassini mission have observed that Saturn's largest moon, Titan, behaves much like Venus, Mars or a comet when exposed to the raw power of the solar wind. ...

NASA engineer advances new daytime star tracker

18 hours ago

Scientists who use high-altitude scientific balloons have high hopes for their instruments in the future. Although the floating behemoths that carry their instruments far into the stratosphere can stay aloft ...

User comments : 0

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.