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29 February , 2008
ARLP009
A sunspot emerged a few days ago, a welcome sight at cycle minimum.
Sunspot numbers for February 25-28 were 12, 13, 12 and 12, but that spot (number 983) is now gone, over the eastern horizon of our Sun.
If the February 29 sunspot number is 0, this means our three month moving average of sunspot numbers centered on January will be 8.5, slightly higher than the last reading. Our moving average centered on June 2007 through January 2008 is 18.7, 15.4, 10.2, 5.4, 3, 6.9, 8.1 and 8.5, with the minimum centered on October 2007.
A 13-month predicted smoothed sunspot table from NOAA at http://www.swpc.noaa.gov/ftpdir/weekly/Predict.txt shows a combination of known and projected values. On February 6, when this was released, the August 2007 value represents mostly known values, because January's actual sunspot numbers are known. All that is missing is February, which has a predicted value, averaged in with the previous months. November's value is made up with three fewer months of actual values. Next week a new table should be released.
Remember that a sunspot number does not represent the actual number of sunspots. The minimum non-zero sunspot number is 11, because a value of 10 is counted for each cluster of sunspots, and a value of 1 is added for each individual spot. So the February 26 sunspot number of 13 represents one group containing three sunspots.
This week geomagnetic conditions have been quiet, until yesterday when the effects of a solar wind stream were felt, taking the planetary A index to 22 and K index as high as 4. This moderate disturbance should decline, with a predicted planetary A index at 15, 10 and 5 for January 29 through March 2. Our next unsettled period should be March 8, 9 and 12. Geophysical Institute Prague predicts unsettled to active conditions February 29, unsettled March 1-3, quiet to unsettled March 4, and quiet March 5-6.
For the ARRL International SSB DX Contest this weekend conditions should be good (no geomagnetic storms), but probably no sunspots.
We are just a few weeks away from the Spring Equinox, always a great time for HF propagation. It would be nice to have some sunspots as well.
Last week's bulletin contained an erroneous explanation about discerning the difference between Cycle 23 sunspots and the new Cycle 24 spots. Tom Lizak, K1TL of Tiverton, Rhode Island caught this. The information given was only true for the Sun's northern hemisphere. Southern hemisphere spots have exactly the opposite orientation of spots north of the Sun's equator. Also, new Cycle 24 spots should appear away from the equator in the early part of the cycle.
Go to http://sohowww.nascom.nasa.gov/data/realtime/
mdi_mag/512/ to look at the latest magnetogram. For February 28 you can see some white and black spots, but these represent magnetically active areas. Real sunspots will have the white and black areas together.
You can search recent archives to display magnetograms prior to the current ones by clicking on the link for Search Real Time Data.
There you can enter a range of dates in the YYYY-MM-DD format, choose the resolution you want, (512 or 1024), and select the MDI Magnetogram image type.
We had some good propagation reports this week, including sporadic-E propagation on 6 meters. Dan Eskenazi, K7SS in Seattle, reported 10 and 6 meter E-skip for February 25-26. On 6 meters he worked Utah, Nebraska and Kansas, reporting that the stations he heard were very loud.
Jon Jones, N0JK reports that on February 26, around 0300z XE2WWW (in grid square EL06) worked all call areas in the contiguous 48 states except for 1, 2 and 3. Jon also heard VE3KP take advantage of an e-layer link to the F2 layer. He worked VP6DX in Ducie on 6 meters.
Jon said the 6-meter opening lasted from 2200z February 25 until after 0500z February 26, "seven solid hours of E-skip."
On February 24 Jon wrote, "VP6DX's consistent coverage of 10 and 12 meters, high power and good antennas allow the MUF to be tracked with reasonable precision. Today for example, the 12 meter SSB and CW stations were booming into Kansas at 2100 UTC. Yet the MUF fell short of 28 MHz. But a few minutes later the 10 meter station could be heard weakly, almost like 6 meter scatter. One can review the packet cluster spots for VP6DX on various bands and get an approximate view of the MUF and LUF between Ducie and various parts of the world. Even different parts of the lower 48 states experience different propagation. Florida, Texas and California seem to have far more 10 meter propagation to Ducie than other parts of the country."
Joe Reisert, W1JR of Amherst, New Hampshire sent an interesting report about fun he had recently with QRP.
Joe wrote, "The last two weeks have been pretty exciting for DX'ers. The Ducie Island DXpedition operating as VP6DX gave us all lots of time for checking propagation over a reasonable distance. It also gave lots of moderate to down right small stations a chance to try out their gear and see if they could work a real rare DXCC entity."
He continued, "I decided to see how well VP6DX was able to hear QRP. By the time they shut down, I had worked them on CW, SSB and RTTY all with only 4 watts at my transmitter. Next I tried different bands with QRP. When I finally worked them on a rare (at this time of year) Sporadic E opening on 10 meters, I had a two way with them on all eight bands from 80 through 10 meters in less than 2 weeks.
This was all done with modest antennas such as a 3 element Yagi up only 50 feet and never exceeding 4 watts at the transmitter. My hat goes off to the superb VP6DX operation. It shows what can be done with a small station."
Last, please check out this offering from Microsoft Research, an online telescope at, http://www.worldwidetelescope.org. Not quite ready yet, but soon it could be a wonderful tool.
If you would like to make a comment or have a tip for our readers, email the author at, k7ra@arrl.net.
For more information concerning radio propagation, see the ARRL Technical Information Service web page at, http://www.arrl.org/tis/info/propagation.html.
For a detailed explanation of the numbers used in this bulletin see, http://www.arrl.org/tis/info/k9la-prop.html.
An archive of past propagation bulletins is at http://www.arrl.org/w1aw/prop/. Monthly propagation charts between four USA regions and twelve overseas locations are at http://www.arrl.org/qst/propcharts/.
Sunspot numbers for February 21 through 27 were 0, 0, 0, 0, 12, 13 and 12 with a mean of 5.3. 10.7 cm flux was 71.8, 72.4, 71.6, 70.7, 71.4, 70.7, and 70.7 with a mean of 71.3. Estimated planetary A indices were 6, 4, 4, 3, 3, 3 and 12 with a mean of 5. Estimated mid-latitude A indices were 3, 3, 3, 2, 1, 2 and 6, with a mean of 2.9.
Source: The
American Radio Relay League
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