Quite a few websites, blogs, and discussions are using the NOAA 'preliminary' data of days during which no sunspots can be seen on the Earth-facing solar surface. The last period of blank-Sun days ended on September 1, 2009. According to NOAA's preliminary record, the Sun was blank for 50 days.

However, NOAA's record is preliminary, and may be adjusted. A more accurate record is kept by the 'official' record-keepers of sunspot counts, the SIDC - Solar Influences Data Analysis Center.  Based on their official report for July 2009 (see the full report), a sunspot occurred on July 23, and again on July 30, 2009.  The number of days between July 30 and September 1, 2009 is 32 days.

So, by official count (and remember, the SIDC daily record that includes these two sunspots is included in the official Provisional Monthly Sunspot Number), the last run of zero sunspots was not 50 days, but only 32 days.  This goes against the sensational reports that this last quiet spell was nearly a record-long quiet.

For the record, the longest known quiet run was April 8, 1913 through July 8, 1913 (91 days).  This last quiet period ranks at about 15th longest since 1849, the year that accurate daily sunspot counts have been kept.  During this current cycle transition between Sunspot Cycle 23 and Cycle 24, however, this last run of spotless days is the longest, by one day.  That run was from July 21 through August 20, 2008.  But, don't let the sensationalists convince you that this last run is historical.  Other cycles have had longer runs.

What does all of this mean?  Clearly, there is another cycle (or perhaps more than one other cycle) at work (at least, we think there are other cycles) besides the 22-year magnetic cycle to which the 11-year average cycle belongs.  Some suggest that there is a 200 to 250 year cycle where we see very low sunspot activity (Maunder Minimum was one of those).  Others see possible longer-term cycles. (See The Spotless Page)

There is a lot of speculation going around that we're about to enter a phase of the solar cycle in which the solar energy will be very low.  Will this result in a cooling of the Earth?  We'll report on research and current discussion points, in up-coming podcast episodes.  Be sure to subscribe to our podcast.

Some Question the Data in the 2006 Livingston/Penn Paper

Tomas David Hood (NW7US), the director of HFRadio.org and producer/co-host of the NW7US Space Weather and Radio Propagation Podcast, has received correspondence from a number of individuals that calls into question the research discussed in Episode 4 of the Podcast.  For example:

"In the 2006 journal article, I found the last sentence of the first paragraph of Observations troubling:  1.  If no effort is made to prevent counting the same sunspot twice, one could, even subconsciously, favor sunspots that might favor one's hypothesis and 2.  If multiple counting is allowed and long-lived sunspots have different characteristics than shorter-lived sunspots, the data is skewed toward sunspots with longer lives because there are more opportunities to count these sunspots, more times.  If I were a reviewer of this paper, I would be very uncomfortable with this sentence."

Tomas asked Dr. M. Penn, one of the authors of the 2005 paper, about this issue.  Penn responds:

"As you know the Sun is highly dynamic!  The following movie from MDI on SoHO of the 2001 sunspots dramatically shows this:

http://soi.stanford.edu/press/ssu11-01/MPG/Ic.2001.mpg

Bill's observations occur only 60 days per year, so with clouds, he might have 50 snapshots of the sunspot activity during this movie.  Small pores evolve from hour to hour, and even large umbrae change from day-to-day and week-to-week.  His observation plan minimized bias by measuring every sunspot on the visible disk each day he observed.  Without continuous observations, it's impossible to tell if a particular pore has been observed already; and worse, without seeing the far-hemisphere of the Sun, it's impossible to tell even if large umbrae appearing on the eastern limb have been observed on their previous rotation.  Equally important is the fact that not all sunspots could be observed.

Selection bias was extensively tested in this and following work.  Larger sunspots tend to live longer and thus have a higher probability of being observed multiple times.  The data sets were examined to measure the behavior of different-sized spots, and each size bin showed the same time variation; large spots by themselves showed the same trends that small spots by themselves showed.

We know the sample is incomplete, but with the testing we've done we think that multiple measurements do not introduce a bias which would cause the time variation.

As far as an observer-introduced bias... Bill is internationally known as a very patient and excellent observer.  It's hard to imagine that during the course of 13 years he (consciously or not) subtly changed his sunspot selection to introduce a linear trend, and further that his personal bias would eventually agree with the fact that the next solar minimum would be longer than usual!  Furthermore, current work on automatically selected sunspots from archival data bases supports these IR observations."

Reference:

Episode 4: Disappearing Sunspots by 2015?

Ending a rather long period of sunspot inactivity, a new sunspot appeared on 31 August, 2009.  At the time of writing this report, the active region, numbered by NOAA as AR 11025 (or, simply, 1025), has two sunspots in this one active region group.  However, in images seen so far by this author, it appears to not have a penumbra, only an umbra.  As new images become available, and as solar observations are reported by observations such as Catania, we will be able to refine this determination.  It currently has a Beta configuration.  Very minor flaring is occurring.

We're pleased to present: Episode #4 of the NW7US Space Weather and Radio Propagation Podcast.

How to Listen to This Podcast Episode

Details About This Podcast

In this episode, Amateur Radio Operator, Tomas David Hood (NW7US) discusses with Dr. Penn of the National Solar Observatory the startling yet convincing trend revealed in research of magnetic strengths of sunspots over the last thirteen years. The trend indicates a strong possibility, if the trend continues, that sunspots will disappear by the year 2015!

Additionally, space weather and propagation conditions through August are reviewed, and the outlook for this coming week is presented.

Do you have any thoughts, suggestions, comments, or questions about this podcast, or of the podcast, in general? Please use the feedback form to send your correspondence to Tomas, NW7US.

A version of this podcast will be made available in a format ready for amateur radio repeater and HF transmission in the form of an information bulletin package. Details will be posted at the main Podcast website.

Dr. Matthew Penn

Image of Dr. Matthew Penn - In this picture, Dr. Penn is working with the the NSO Array Camera, which is the workhorse infrared detector at the McMath/Pierce Solar Telescope. Penn uses it to map the magnetic fields in sunspots using sensitive infrared spectral lines, as well as for studies of the solar atmosphere.

Papers and Articles by M.Penn

New - September 2, 2009: Dr. Penn responds to a general question regarding data integrity.