Thursday, July 16, 2009

Where Have All the Sunspots Gone?

If you look at the sun today (or let a hundred million dollar satellite look at it for you) you'll see something like this:
In fact if you would have looked at the sun almost anytime in the past 6 months, you would have seen that same thing. Why is that worthy of a blog post? Because there are no spots. In fact as of right now there hasn't been a sunspot for 5 days. If you look at a plot of recent sunspot activity, like the one below, you'll see that there hasn't been much happening on the sun for a while now. It's expected that we won't have a lot of sunspots right now because we are currently in solar minimum (the bottom of the solar cycle).

However, if you compare the number of sun spot-less days in the current solar minimum with the last one in 1996, it is easy to see (if you click of the graph, sorry for the small size) that something odd is going on this time around.For some reason in this solar minimum there are far fewer sun spots than last time. In fact, this is shaping up to be the weakest solar cycle since the 1920's. What would be really exciting, however, would be if the solar cycle actually shut off for a while as it appears to have done in the late 1600s. For those of us in the solar dynamo community, it's fun to have a little bit of variety in our lives even if that variety means nothing is happening.


  1. I'm glad you guys have some interesting things to think about. I for one am interested in the sun spot issue, but only have an elementary understanding of the whole thing.

    Nick, how long to individual sun spots last? Is it on the order of days, weeks years? Do you remember what the sunspot rate was in that unusual period in the 1700s?

    If I was a "pork barrel" barrel politician I would have said: "We spent hundred million dollars to take this picture". That, of course, would be disingenuous, but then I would fit in with a lot of politicians.

    Who was it complaining all campaign that we spend millions of dollars to study flies forgetting to mention those fruit flies are some of the cheapest, most efficient ways to find new ways to understand human biology/cure diseases/etc...? Um, I think someone who is now resigning as governor somewhere.

  2. Joe,

    Individual sunspots last on the order of 20 days, but show marked evolution as they age.

    During the period in the 1600's that I mentioned (which is known as the Maunder minimum) we don't have daily sunspot records (which we have everyday without exception since 1848), but reconstruction based on partial records (usually on the order of 10 days per month) it looks like the average sunspot number was on the order of 1. In the last solar maximum the sunspot number was about 70. The Maunder minimum is a real puzzle because we have records of other times when cycles were small, but it appears to be the only time when they simply shut off.

  3. It's amazing (to me) that we have daily records since 1848. I need to give those 1800s scientists more credit.

  4. I agree. They set up a network of more than 20 stations all over the world (mostly in the British Empire) that each made observations each day in order to assure that not all of them could be stopped by clouds. And they collected these observations by mail. It's amazing it all worked.

  5. Luckily SOHO has taken something close to a million observations of the sun in roughly 10 bands, so each picture is only about $10. And aside from that they developed some amazingly small Michelson interferometers as a part of this mission. Lockheed, which built the interferometers, has actually been able sell the design to several companies that make passive spectrometers in things like chemical detectors.

    Add to that the fact that the SOHO spacecraft just turned 14 and was only supposed to live 5 years and this one is really not the mission politicians should be coming after. I hear fruit fly research is a good target... :)


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