What is the Solar minimum? What we are talking about are sunspots or the lack of sunspots. This has been a very boring last couple of years. The sun has many cycles. The Schwabe cycle lasts about 11 years normally. This cycle tracks sunspots from maxima to minima. Just like everything else in this world there are quirks to this Cycle. We are in a very deep minimum right now,13 years and going... It is the deepest in fifty years! one of the deepest since 1913.Take a look at this graph, Credit: David Hathaway, NASA/MSFC. There were 0 observations of sunspots for 266 of 366 days in 2008. That's 73% my friends. In those 100 days of spots there were only 30 sunspots produced. 60 t0 150 spot are the norms for most Cycles. So far this year we are at 10 sunspots since June. So far this July we have had some activity and there are rumblings in the Helio community this might be the end of Cycle 23 (Schwabe). We shall see on that one...Cycles... speaking of Cycles,there have also been detected a 22 year Hale, 80 year Gleissberg, 200 year Suess, and 2,300 year Halstatt cycle of solar activity.
We need to explore a little to get a good picture of why this could be a big deal. There is strong evidence to support a correlation between sunspot cycles and climate change. I always tend to cast doubt on number crunching as you can pretty much prove your point or disprove your point using the same data in most cases. I know this summer has been a mild one to be sure. Is this due to a minimum of sunspots? Not only has there been a lack of sunspot activity but also in other areas of Solar behavior. The luminosity of the Sun has dimmed a bit. Measurements by several NASA spacecraft show that the sun's brightness has dropped by 0.02% at visible wavelengths and 6% at extreme UV wavelengths since the solar minimum of 1996. That is a 12 year low. We are at a 50 year low in solar wind pressure which is a big deal if you are an Astronaut . Solar wind tends to keep the cosmic radiation down around the inner planets. That also means less geomagnetic storms too. I miss a good Auroral display. To Ham radio operators the skip just ain't what it used to be. The ionosphere (a reflective layer for radio waves) has not been as ionized so less reflective. Radio emissions by the sun are also at a 55 year low which means at least it is quieter.
To look at some of this evidence for the correlation, we have to set the Way On Back Machine to between 1645 and 1715. This was the Maunder Minimum, a 70 year period characterized by a nearly complete absence of sunspots which coincided with the “Little Ice Age” in Europe, a time of especially long and cold winters. There was actually a year without a summer. Writings of the time indicate this. Proof can also be seen in ancient trees as growth rings showed problems during this time. This is the extreme. The 200 year Suess cycle is expected to reach minimum around 2040. There have been predictions of a long lasting and gradual decrease in global temperatures over the next century. (Note to Global warmers) regardless of the amount of carbon dioxide in the atmosphere. In 1991 Danish meteorologists Eigil Friis-Christensen and Knud Lassen published a paper titled “Length of the Solar Cycle: An Indicator of Solar Activity Closely Associated with Climate.” They pointed out the length of the Schwabe solar cycle and global mean temperatures were related. They noted that longer cycles of 12-14 years produced cooler global temperatures and short 9-10 year cycles led to warmer climates. Lots of scientists made note of that.
For me as an Astronomer this means one very important thing... The Sun is a very boring piece of work right now. Take a look at this picture from today! I just bought this Sun filter for my 8" Celestron. Not one of those expensive 1000 dollar filters ,but a modest Baader solar film white light filter It lets me see Sunspots, and Faculae.These are features associated with solar activity. Faculae are bright patches of magnetic activity. in times of solar maximum they can increase the brightness (visual) of the Sun by 0.1 percent. I can also see Granules. They are rice kernel looking features that cover the entire sun. Granules are the tops of convection cells where liquid is pushed to the surface of the sun where it cools and is continually replaced by newer cells coming to the surface. I did catch a Sunspot on Friday a few weeks ago but they have been far and few between
Someone on Facebook asked me what a sunspot was. The short version is It is a magnetic eruption in the solar disk. You will usually see two groups at a time. One being magnetically opposite to the other, like the two ends of a bar magnet. The center, called the umbra is much cooler (relatively) 3700 K as opposed to 5700K for the rest of the surface of the sun. It will still give you a hot foot! Look at the center of this sunpot in the picture, this is where the strongest area of magnetismis located. The outer greyish areas are called the penumbra This is where you see some very cool looking prominences. A prominence is a loop of material transferred from one spot to the other via the magnetic field.
So is it all connected ? Maybe maybe not. Time will tell as it always does. In the mean time I will continue to go out side set my scope up take a look at the sun and say Rats! No spots again. I will say this about the present minimum The good folks out in Arizona have detected a jetstream inside the sun and have been tracking this thing. When this jet stream reaches the 22 degree lattitude sunspot activity increases. I have my Filter at the ready until then. For right now, the forecast for Sunspot activity is kind of spotty at best. (Sorry could not resist )
Clear skies and Great seeing too