Reprinted from NOAA Magazine
2007 April 26
April 26, 2007 — All eyes are on the sun (though not directly with the naked eye) now that the NOAA-led Solar Cycle 24 Prediction Panel released its official consensus solar cycle forecast at the Space Weather Workshop in Boulder, Colo., yesterday. The panel agreed that the Earth will soon experience a period of intense solar storms and the exact number of solar storms expected will become clearer in time.
"The next 11-year cycle of solar storms will most likely start next March and peak in late 2011 or mid-2012," said Doug Biesecker, a solar physicist from the NOAA Space Environment Center in Boulder, Colo., who also chaired the NASA-funded 12-person panel.
Although the effects of solar storms are often seen from Earth as beautiful lights dancing in the night sky (i.e., the Northern Lights or aurora borealis), looks can be deceiving. In reality, these storms can carry tremendous power and travel at speeds up to 5 million miles per hour. Solar storms have been known to knock out satellites, power supplies, communications and navigation systems. Many of these effects are transitory (and virtually invisible), but they can be very disruptive and potentially dangerous — both to the systems themselves and in turn the nation's economy. Damage to these systems can also result in secondary effects that can disrupt virtually every major infrastructure dependant on them, including transportation, security and emergency response systems, telecommunications and other wireless networks and electronic equipment. Solar storms even create a biological threat to both astronauts and people flying in aircraft at high altitudes and latitudes.
Therefore, the Solar Cycle 24 Prediction Panel's forecast is being used by various industry and government groups for planning purposes, including power companies, communication networks, satellite manufacturers/operators and airline flight planners. Unfortunately, the nation's (and the world's) vulnerability to solar storms will only increase as we become even more dependant on these technologies.
"As people become more dependent on space-based technology, the potential far-reaching and dramatic impacts of space weather make our mission more vital each day," said Bill Murtagh, a space weather forecaster at the NOAA Space Environment Center in Boulder, Colo. "Accurate space weather measurements and predictions are vital in mitigating the potential impact of these storms."
"The Space Environment Center's space-weather alerts, warnings, and forecasts are a critical component of NOAA's seamless stewardship of the Earth's total environment, from the sun to the sea," said retired Vice Adm. Conrad C. Lautenbacher, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator.
The NOAA SEC is the nation's first alert of solar activity and its affects on Earth. Just as NOAA's hurricane experts predict the upcoming season of Atlantic storms and forecast individual hurricanes, the agency's space weather experts issue outlooks for the next 11-year solar "season" and warn of storms occurring on the sun that could impact the Earth. Both the NOAA National Hurricane Center and SEC are among NOAA's nine National Centers for Environmental Prediction. SEC is also the world warning agency of the International Space Environment Service, a consortium of 11 member nations.
NOAA Perspectives on the Solar Cycle 24 Forecast
"The prediction process was much more challenging than the previous two solar cycle forecasts because it was conducted much earlier in the cycle and because of the wide array of predictions that needed to be reconciled this time around," stated Biesecker. In all, the panel evaluating more than 40 predictions from 15 different nation — some predicting a small solar cycle with as little as 42 sunspots, while others predicted a larger cycle with up to 185 sunspots (which would nearly rival the record setting Cycle 19 observed in the 1950s).
"Since we have not even reached the solar minimum or end of this solar cycle , we were really pushing the envelope on this one," said Biesecker. "Solar cycle predictions are fairly reliable once the cycle is underway, but prior to that time the predictions are less certain — although equally important."
"The predictions for the strength of Solar Cycle 24 had more than a threefold difference among them — that's a tremendous range," says Murtagh. "Satellite design and mission planning teams and other end users aren't always able to sort through all the conflicting information, so it is up to the NOAA Space Environment Center and the rest of the panel to come up with a single official prediction upon which they can base their decisions."
The Science Behind the Predictions
Eleven-year solar cycle forecasts predict the number of sunspots which will occur during a given solar cycle, and sunspots are known to generate solar storms that could potentially damage Earth systems. Like other long-term weather forecasts, the solar cycle forecast does not predict the time, intensity or duration of the solar storms. In this way, the solar cycle forecast is very much like NOAA's seasonal hurricane outlook — the overall level of activity for the season is forecast, but it doesn't predict the specific time, intensity etc. of any given storm. That is covered by more short-term space weather warnings issued by the NOAA the NOAA Space Environment Center.
Each 11-year solar cycle consists of a solar maximum characterized by a large number of sunspots (and solar storms) followed by a solar minimum characterized by a smaller number of sunspots (and solar storms). Currently, we are approaching the end of Solar Cycle 23 (a solar minimum) and are on the heels of the start of Solar Cycle 24 (a solar maximum) — so the topic on the minds of many people is the upcoming Solar Cycle 24, its much anticipated solar maximum, and the number of solar storms it will generate.
The sun, like Earth, has seasons. The sun's season is dictated by sunspots and is known as the 11-year solar cycle. Sunspots occur when strong magnetic fields emerge through the solar surface and allow the area to cool slightly, thus making it appear as a dark spot in contrast to the even hotter sun areas surrounding it. These magnetically disturbed regions are often the source of large solar flares and coronal mass ejections from the sun.
At the beginning of each 11-year solar cycle, sunspots first appear at high latitudes, but as the cycle continues, sunspots start emerging closer to the equator and eventually stop forming all together as the cycle comes to a close. Sunspots only last for a few weeks and are basically tangled knots of magnetism generated by the sun's "inner dynamo" (i.e., the internal engine that powers/drives the sun). Throughout their life, they decay, leaving behind weak magnetic fields as their 'remains.' Then the sun's "dynamo conveyor belt" (similar/analogous to the one that drives ocean circulation on Earth, only it is made up of gas on the sun) comes along and skims the surface of the sun, sweeping up the magnetic fields of old, dead sunspots. The sunspot 'remains' are dragged toward the poles and then down to a depth of 200,000 km where the sun's magnetic dynamo (internal engine) reenergizes (essentially reincarnates) them. Once the sunspot 'remains' are reincarnated, they become buoyant, float back to the surface and create a brand new sunspot! It takes about 40 years to perform one complete circuit because the sun's conveyer belt only moves at a rate of about one meter per second. Researchers believe the turning of the belt — especially the speed of the belt — controls the sunspot cycle.
"It is very dynamic, but basically the sun's dynamo conveyer belt 'recycles' old sunspots from the current (or previous) solar cycle(s) to form seeds which germinate new sunspots during next (upcoming) solar cycle," said Biesecker. "It is important to understand this, because the sun's 'dynamo conveyor belt' forms the basis for many of the predictions used in the panels final Solar Cycle 24 forecast."
Solar Cycle 24 Predictions and the Prediction Process
"Although they are too complex to describe in detail here, there are approximately six techniques used to predict the intensity of a solar cycle," said Biesecker. "The first three are based on statistics and provide a sound historical baseline upon which to forecast future cycles. The other three are based on physics and the sun's dynamo conveyer belt theory."
Like the previous two solar cycle predictions, the final Solar Cycle 24 forecast was based on various combinations of several of these techniques, however there was a tendency to rely less on statistical techniques and more on physical techniques. It is important to note, however, that the physical techniques are still relatively new, full of uncertainties and part of a new field of research NASA is studying called helioseismology (which is analogous to studying earthquakes on Earth).
"The biggest question right now is when will we reach the solar minimum for the current Solar Cycle , because that will essentially mark the start of Solar Cycle 24," said Biesecker. "It will serve as a good 'litmus test' for the validity of the models used in making the final prediction. If a given model fails to accurately predict the start of Solar Cycle 24, then it is likely that it will also fail to accurately predict the timing, duration and intensity of the cycle's peak [solar maximum] and may therefore need to be eliminated from future [updated] Solar Cycle 24 predictions. Therefore, as the cycle progresses and we get more data, the panel will need to reevaluate its original predictions and periodically [annually] update it over the next few years."
According the Biesecker, we will have a better idea of what solar weather has in store for us in late 2008 when Solar Cycle 24 is on the rise.
Relevant Web Sites
NOAA Space Weather Week - SEC's Annual User Conference
NOAA Space Environment Center
Space Weather Now
Today's Space Weather
NOAA Primer on Space Weather
Space Environment Center Education Web site
The Growing Importance of Space Weather Information
Solar Storms Cause Significant Economic and Other Impacts on Earth
NOAA Space Environment Center: Earth's First Defense Against the Sun's Fury
This story was originally titled "All Eyes Are On The Sun After NOAA-Led Solar Cycle 24 Panel Predicts Upcoming Period Of Intense Solar Storms".
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