NASA Earth Observatory
April 1, 2009: The sunspot cycle is behaving a little like the stock market. Just when you think it has hit bottom, it goes even lower.
2008 was a bear. There were no sunspots observed on 266 of the year’s 366 days (73%). To find a year with more blank suns, you have to go all the way back to 1913, which had 311 spotless days: plot. Prompted by these numbers, some observers suggested that the solar cycle had hit bottom in 2008. Maybe not. Sunspot counts for 2009 have dropped even lower. As of March 31st, there were no sunspots on 78 of the year’s 90 days (87%). It adds up to one inescapable conclusion: “We’re experiencing a very deep solar minimum,” says solar physicist Dean Pesnell of the Goddard Space Flight Center.
“This is the quietest sun we’ve seen in almost a century,” agrees sunspot expert David Hathaway of the Marshall Space Flight Center.
The current solar minimum is part of that pattern. In fact, it’s right on time. “We’re due for a bit of quiet- and here it is,” says Pesnell. But is it supposed to be this quiet? In 2008, the sun set the following records:
A 50-year low in solar wind pressure: Measurements by the Ulysses spacecraft reveal a 20% drop in solar wind pressure since the mid-1990s – the lowest point since such measurements began in the 1960s. The solar wind helps keep galactic cosmic rays out of the inner solar system. With the solar wind flagging, more cosmic rays are permitted to enter, resulting in increased health hazards for astronauts. Weaker solar wind also means fewer geomagnetic storms and auroras on Earth.
A 12-year low in solar “irradiance”: Careful measurements by several NASA spacecraft show that the sun’s brightness has dropped by 0.02% at visible wavelengths and a whopping 6% at extreme UV wavelengths since the solar minimum of 1996. These changes are not enough to reverse the course of global warming, but there are some other, noticeable side-effects: Earth’s upper atmosphere is heated less by the sun and it is therefore less “puffed up.” Satellites in low Earth orbit experience less atmospheric drag, extending their operational lifetimes. That’s the good news. Unfortunately, space junk also remains longer in Earth orbit, increasing hazards to spacecraft and satellites.
A 55-year low in solar radio emissions: After World War II, astronomers began keeping records of the sun’s brightness at radio wavelengths. Records of 10.7 cm flux extend back all the way to the early 1950s. Radio telescopes are now recording the dimmest “radio sun” since 1955: plot. Some researchers believe that the lessening of radio emissions is an indication of weakness in the sun’s global magnetic field. No one is certain, however, because the source of these long-monitored radio emissions is not fully understood.
All these lows have sparked a debate about whether the ongoing minimum is “weird”, “extreme” or just an overdue “market correction” following a string of unusually intense solar maxima. “Since the Space Age began in the 1950s, solar activity has been generally high,” notes Hathaway. “Five of the ten most intense solar cycles on record have occurred in the last 50 years. We’re just not used to this kind of deep calm.” Deep calm was fairly common a hundred years ago. The solar minima of 1901 and 1913, for instance, were even longer than the one we’re experiencing now. To match those minima in terms of depth and longevity, the current minimum will have to last at least another year.
In a way, the calm is exciting, says Pesnell. “For the first time in history, we’re getting to see what a deep solar minimum is really like.” A fleet of spacecraft including the Solar and Heliospheric Observatory (SOHO), the twin STEREO probes, the five THEMIS probes, ACE, Wind, TRACE, AIM, TIMED, Geotail and others are studying the sun and its effects on Earth 24/7 using technology that didn’t exist 100 years ago. Their measurements of solar wind, cosmic rays, irradiance and magnetic fields show that solar minimum is much more interesting and profound than anyone expected.
Modern technology cannot, however, predict what comes next. Competing models by dozens of top solar physicists disagree, sometimes sharply, on when this solar minimum will end and how big the next solar maximum will be. Pesnell has surveyed the scientific literature and prepared a “piano plot” showing the range of predictions. The great uncertainty stems from one simple fact: No one fully understands the underlying physics of the sunspot cycle. Pesnell believes sunspot counts will pick up again soon, “possibly by the end of the year,” to be followed by a solar maximum of below-average intensity in 2012 or 2013. But like other forecasters, he knows he could be wrong. Bull or bear
As a physicist, you will be well aware of the solar interaction with the magnetosphere. More solar activity, more energy expended by the earth’s magnetic field and upper atmosphere diverting this energy past the earth. Work done energy transfer etc. I do not like the arguments for global warming not existing/not us that are provided by most of the web bloggers etc as they tend to jump on any band wagon going, very much like the save the earth people. Anyone that takes what they read without thinking about it does not deserve to be heard. This is taking my own experience (and space science degree) and applying it to the published papers that I find, and I do try and look for them. Almost every global catastrophe paper that I have read is based on a small environment measured. (Arctic snow fall, desert rain fall, sea rise in San Marino etc). Almost all of these studies work on the basis that solar radiation is a constant. This may largely be the case, but we have no worthwhile data for this by the way, first satellite that measured it was about 1985 with decent accuracy and we have nothing to compare against. Also if we could work out any of the energy transfer systems that are existent on earth then I would be very impressed. People who have data spanning a 50 year period and have drawn conclusions are deluded. Give me any data set over a short period and I can present it any way you like. You must remember experimental physics at uni!! Of all energy put into the earth’s atmosphere, and I will guess at this point, and go for 1.4KW/m2, a figure researched. That is as much as a small electric fire place in every square metre of the earths surface and turned on. This is by sunlight. If this energy is not being transferred by virtue of solar wind transfer then it will undoubtedly cause fluctuations in the earth global temperature. I do not want to say that we are not destroying the planet. I believe that we are. But what we are concentrating money on is not going to be the solution. Carbon credits will only add to the global financial problem. If we wish to have less impact then we need to stop breeding. I have no doubt nature will find a way to stop us doing so in the future!!