Another Day Without Any Sunspots
Carl Luetzelschwab K9LA
As of Saturday November 3, we have had 27 consecutive days without any sunspots. This latest run started
on October 8. Prior to this we had a run of 21 days with no sunspots (September 7 through September 27).
Is this unusual to have so many days without any sunspots at solar minimum? Not really. For example,
between Cycle 22 and Cycle 23 we had a run of 42 days with no sunspots (September 13, 1996 through
October 24, 1996). And does the length of consecutive days with no sunspots tell us anything about the
maximum of the next cycle? That.s easy to determine by looking at historical data.
Solar minimum
between Cycles
Greatest number of consecutive
days without any sunspots
Maximum smoothed sunspot
number of next cycle
17 and 18 36 (18Apr1944 23May1944) 152 (Cycle 18)
18 and 19 30 (31Jun1954 2Jul1954) 201 (Cycle 19)
19 and 20 15 (15Sep1964 29Sep1964) 111 (Cycle 20)
20 and 21 24 (8Jul1976 31Jul1976) 165 (Cycle 21)
21 and 22 21 (23Dec1985 12Jan1986) 158 (Cycle 22)
22 and 23 42 (13Sep1996 24Oct1996) 121 (Cycle 23)
A quick glance at the data suggests no correlation, as the biggest cycle (Cycle 19) had more consecutive
days without any sunspots than three smaller cycles (Cycles 20, 21, and 22). Doing a scatter plot of the
number of consecutive days versus the maximum smoothed sunspot number of the next cycle confirms this.
maximum smoothed sunspotnumber of next cycle
225
200
175
150
125
100
R2 = 0.0041
10 15 20 25 30 35 40 45 50
consecutive days at solar minimum with no sunspots
The blue triangles are the six data points, and the red line is a best-fit linear trend line. The R2 value in the
upper right indicates the correlation. A value of 0 is no correlation, and a value of 1 is perfect correlation.
The R2 value of 0.0041 says there is no correlation.
If we haven.t had any sunspots for 27 days (and counting), why have we had such good propagation
recently on the higher bands (for example, on 15m during CQWW Phone)? There are three reasons for this.
First, sunspots (along with 10.7 cm solar flux) are proxies for the true ionizing radiation of the F2 region
(wavelengths of 10 to 100nm) so they don.t tell the true story (especially on a day-to-day basis). Second,
we.re moving into the fall and winter months, and a change in the composition of the upper atmosphere
results in higher daytime F2 region maximum usable frequencies. And third, the day-to-day variability of
the F2 region depends more on geomagnetic field activity and events in the lower atmosphere coupling up
to the ionosphere than on small changes in solar radiation. With 15m being borderline good-bad around
solar minimum, any geomagnetic field activity and/or traveling ionospheric disturbances could push the
maximum usable frequency up enough to give life to 15m on certain .good..days. This appears to be what
happened for CQWW Phone (more details on this will be in the January/February issue of The National
Contest Journal).
0 comments:
Post a Comment