What’s Wrong with the Sun? (Nothing According to NASA)
Science@NASA, 07.11.2008 [here]
Stop the presses! The sun is behaving normally.
So says NASA solar physicist David Hathaway. “There have been some reports lately that Solar Minimum is lasting longer than it should. That’s not true. The ongoing lull in sunspot number is well within historic norms for the solar cycle.”
This report, that there’s nothing to report, is newsworthy because of a growing buzz in lay and academic circles that something is wrong with the sun. Sun Goes Longer Than Normal Without Producing Sunspots declared one recent press release. A careful look at the data, however, suggests otherwise.
But first, a status report: “The sun is now near the low point of its 11-year activity cycle,” says Hathaway. “We call this ‘Solar Minimum.’ It is the period of quiet that separates one Solar Max from another.”
During Solar Max, huge sunspots and intense solar flares are a daily occurance [sic]. Auroras appear in Florida. Radiation storms knock out satellites. Radio blackouts frustrate hams. The last such episode took place in the years around 2000-2001.
During Solar Minimum, the opposite occurs. Solar flares are almost non-existant [sic] while whole weeks go by without a single, tiny sunspot to break the monotony of the blank sun. This is what we are experiencing now.
Although minima are a normal aspect of the solar cycle, some observers are questioning the length of the ongoing minimum, now slogging through its 3rd year.
“It does seem like it’s taking a long time,” allows Hathaway, “but I think we’re just forgetting how long a solar minimum can last.” In the early 20th century there were periods of quiet lasting almost twice as long as the current spell. (See the end notes for an example.) Most researchers weren’t even born then.
Hathaway has studied international sunspot counts stretching all the way back to 1749 and he offers these statistics: “The average period of a solar cycle is 131 months with a standard deviation of 14 months. Decaying solar cycle 23 (the one we are experiencing now) has so far lasted 142 months-well within the first standard deviation and thus not at all abnormal. The last available 13-month smoothed sunspot number was 5.70. This is bigger than 12 of the last 23 solar minimum values.”
In summary, “the current minimum is not abnormally low or long.”
The longest minimum on record, the Maunder Minimum of 1645-1715, lasted an incredible 70 years. Sunspots were rarely observed and the solar cycle seemed to have broken down completely. The period of quiet coincided with the Little Ice Age, a series of extraordinarily bitter winters in Earth’s northern hemisphere. Many researchers are convinced that low solar activity, acting in concert with increased volcanism and possible changes in ocean current patterns, played a role in that 17th century cooling. … [more]
[The stat babble in this article is misleading. The article states "the ongoing lull in sunspot number is well within historic norms for the solar cycle" but historical norms include long lulls such as the Maunder Minimum. The article states the 142 month decaying Solar Cycle 23 is "within a standard deviation." That is a meaningless statistic since non-linear cycle lengths are not normally distributed.
The word "normal" is used in this article with two different meanings. Statistical normal is not the same as common usage normal. The article confuses the two.
Facts: Solar Cycle 24 still overdue by more than a year and solar magnetic activity is low, indicating that Solar Cycle 24, when it does show up, will be very weak. - Ed]