Solar Science

A blog of solar physics

Archive for April 2008

For some, the waiting is becoming unbearable…

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This just in from Kevin (aka VE3EN) over at solarcycle24.com

Patience is a virtue, Kevin.

Written by John A

April 25, 2008 at 10:31 am

Posted in News and Views

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Fool me

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I look on solarcycle24.com. I see a high latitude sunspot number 992.

spot992-arrow.GIF

I think “hurrah! SC24 has finally shown itself”. I check the magnetogram.

magneto-992-closeup.GIF

The black arrow points to sunspot 992 – and its an SC23 spot! Its the same polarity as the SC23 magnetic signatures further south.

The red arrow points to the reversed polarity SC24 phage left by the tiny SC24 spot left a week ago.

Fool me.

Written by John A

April 23, 2008 at 11:00 pm

Posted in News and Views

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Ken Tapping: The Current Solar Minimum

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I received this via e-mail from K7RA. The original document comes from Dr Kenneth Tapping who was quoted not long ago regarding the solar cycle being “the quietest [he’d] ever seen in 25 years”. This was taken to mean that the current solar minimum was historically unusual, and here Dr Tapping explains that this is not so.

I reproduce here the entire document (other than stylistic changes from PDF to the blog, not a word or a graph has been altered from the original):

The Current Solar Minimum

Ken Tapping, 2008-04-17

This note summarizes my current feeling about the state of solar activity and the solar activity cycle. Any conclusions currently in circulation that have been drawn by extrapolating what you see in this note should not be regarded as reflecting my views. My conclusions are in this note. The information used here is freely available and readers are strongly encouraged to get the data, look at it and draw their own conclusions.

The current solar activity is not that unusual. At this point it is completely unjustified to see current solar behaviour as an indication of any departure from its what the Sun has been doing for at least the last 300 years.

Figure 1 shows a plot of solar activity as measured by the solar radio flux monitors operated by the National Research Council of Canada.

tapping-figure11

Figure 1: Monthly averaged 10.7 cm solar radio flux solar activity index since 1947 (monthly means).

The arrow under the 1964-1977 cycle indicates the length of that cycle, which was a little longer than the others. That same arrow has been copied and put under the last cycle. The length is unchanged. It can be seen that the current solar activity cycle (now ending) has not yet exceeded the length of the 1964-77 cycle. It is also clear that the longish cycle in 1964-77 was followed by further activity cycles – normal solar behaviour. To exceed the duration of the 1964-1977 cycle, the new cycle would have to delay its start at least well into 2009.

Figure 2 shows the 1964-77 and the 1997-? cycles overlaid on the same plot. Once again we can see the last cycle has yet to last longer than the 1964-77 cycle.

tapping-figure-21

Figure 2: The 1964-77 cycles compared. The current cycle (black trace) has yet to last longer than the 1964-77 cycle (red trace).

The 10.7 cm solar flux covers only about six solar activity cycles. Sunspot number data covers at least 300 years. The histogram Figure 3 shows how the durations of the cycles as seen in the sunspot data have varied since 1700. A 13-year activity cycle is not that unusual.

tapping-figure-3

Figure 3: Distribution of solar cycle durations over the last 300 years. The 1964-1977 cycle, having a
duration of 13 years is unusual, but not that unusual.

CONCLUSION: AT THE MOMENT IT IS UNJUSTIFIED TO ASSUME THE SUN IS UNDERGOING A SIGNIFICANT CHANGE IN BEHAVIOUR. ON THE BASIS OF SUNSPOT NUMBER DATA, WE CANNOT ASSUME ANYTHING ODD IS HAPPENING UNLESS THE NEXT CYCLE DELAYS ITS START INTO 2009 OR 2010.

Solar Cycle 24: Do we count Tiny Tims?

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Another week of excitement as the second solar cycle 24 spot appeared…and then disappeared just as rapidly.

I can’t help feeling that with an unprecedented amount of high technology monitoring the Sun with ever higher resolution, the criteria by which a sunspot is defined has become radically weakened to such an extent that it all becomes meaningless.

On Climate Audit commenters noted that the criteria for naming hurricanes had become so weakened that practically any frontal wave in the Eastern Atlantic that persisted for more than a few hours got a name (the so-called “Tiny Tims” of the hurricane season).

So it appears to be with sunspots and Solar Cycle 24. Here is that second solar cycle 24 sunspot numbered for all to see:

mdi_sunspotsgif.jpg

Now in order to ascertain that there really is a spot there, I had to first make sure my laptop screen was really clean because it could have been hidden behind a rogue speck of dust and I could have missed it.

Can you spot it? If so, you’re better than I.

Here’s three views looking at the same spot. It may be there in the magnetogram showing the class signs of magnetic polarity reversal and there may be an associated phage (often the precursor of a sunspot) but is there a sunspot?

spotthesc24spot.jpg

Meanwhile a few days later, yet another SC23 spot comes into view.

I can’t help but feel that this is all a little desperate. SC24 continues to surprise with its general unwillingness to make an unambiguous appearance.

Written by John A

April 19, 2008 at 4:20 am

Posted in Solar Cycle 24

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