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 Previous: Michigan Amateurs Team Up with State |  Next: The Auto-bug Keyer Mark II with Eight Message Memories |
REVISED Mar 17, 2008 10:04 ET
This is an off-schedule propagation bulletin based on last Friday’s release. There will be another off-schedule bulletin on Thursday, March 20, because ARRL headquarters will close for the Good Friday holiday.
The reason for this Monday morning bulletin is to correct some bad data we obtained from issue 1697 of the weekly Preliminary Report and Forecast of Solar Geophysical Data from the NOAA Space Weather Prediction Center. Readers who clicked on the link to issue 1697 in last week’s bulletin may have wondered what we were referring to when we heralded a new prediction for a more robust Solar Cycle 24, and talked about changes from the first week of January forecast in issue 1687.
After I e-mailed a forecaster in Boulder about the new prediction, he responded, “What new prediction?” and he corrected the data Friday morning. Apparently, nobody had noticed the new numbers -- in a table on page 9 of issue 1697 -- when it was released on Tuesday.
I sent my e-mail Thursday night, and I understand they are reviewing the process used to publish these numbers. They said they were so sorry about the mistake and even offered to let me be announcer for a day on the 18-minutes-after-each-hour bulletin of solar flux and geomagnetic data transmitted by WWV if I ever visit Colorado. Can’t be sure if they were serious, but I promised not to use my own call sign.
I understand that currently the numbers for the table are hand-typed, with the data coming from here and here. The first link shows the prediction from the forecast team that believes the next cycle will be robust and the second link is from the group which thinks Cycle 24 will be weak. They have averaged the two predictions. Note that all three tables show a high and low range, reflecting what each team thinks the likely range of values could be.
Note that both teams predict the Cycle bottom was in February 2008. Last month’s value is still a prediction, because these are smoothed sunspot numbers, averaged over a year. February’s numbers are an average of actual monthly numbers for the past six months, and the predicted values for the following six months.
The low team predicts a smoothed sunspot number of 90 at the peak of Solar Cycle 24 in August 2012. The high team says Cycle 24 should peak much earlier in September or October 2011 at 139.9. The average of the two shows a peak of 113.1 in January, 2012.
In the past few days a sunspot has reappeared, with the emergence of sunspot 986. But it is way over on the Sun’s west limb, and will shortly pass from view.
The rest of this bulletin should look familiar. The data at the bottom covers the same March 6-12 time frame and all else is the same, except the comments about a new forecast are deleted.
With just a few scattered sunspots in the past two weeks -- February 28-March 12 -- it isn’t meaningful to ponder the change in weekly averages. There were just four days with sunspots during that time: February 28, March 5-6 and March 10. Sunspot numbers for March 6 through 12 were 12, 0, 0, 0, 12, 0 and 0 with a mean of 3.4. The 10.7 cm flux was 70.3, 70.5, 69.8, 69.5, 70.3, 70.2 and 69.4 with a mean of 70. Estimated planetary A indices were 2, 3, 11, 25, 18, 12 and 14 with a mean of 12.1. Estimated mid-latitude A indices were 2, 1, 6, 14, 12, 7 and 9 with a mean of 7.3.
Regarding those two weeks, why do we report a week of data at the end of this bulletin beginning on a Thursday and ending on Wednesday? Ed Tilton, W1HDQ (SK), a seasoned expert who wrote the bulletin for several decades until early 1991, used a Monday through Sunday reporting week (if I recall correctly) with a weekly bulletin release every Monday morning.
With a change of authors 17 years ago, the bulletin shifted to a Friday release, just in time for increased activity on weekends. We also wanted to present the most recent data, and with a new bulletin written every Thursday night, reporting data through Wednesday seemed the safest choice in case of any problem getting the numbers. At that time, the World Wide Web was just about to be born and most of the data was obtained by dialing up sources over the landline with a 2400 bps modem.
Back then, readers followed the bulletin from W1AW on HF via RTTY, CW or SSB (where it is still transmitted today) or read it locally via packet radio. Today, most readers see it on the Web or receive it via e-mail. By the way, if any reader has an archive of bulletins prior to 1995, please let me know via e-mail.
Chuck Schram, W9UBT, of Scottsdale, Arizona, mentioned that this bulletin hasn’t identified recent sunspots as Cycle 23 or Cycle 24 spots. That’s true, but they were all Cycle 23 sunspots. When we see any Cycle 24 spots, you will read about it here.
For the Short Term
Sunday, March 9 had the highest geomagnetic activity for the week, with the Planetary A index at 25 and Alaska’s College A index at 41. But for many of us, unless we were trying to use HF over a polar path, activity was moderate, with the mid-latitude Fredericksburg A index at 14.
For the short term, the US Air Force Space Weather Forecast Center predicts upcoming sunspot and solar activity just as low and uneventful as it was recently. The next time a solar wind stream is expected to drive geomagnetic activity to the same level as March 9 is March 26-28, with the highest activity predicted for Thursday, March 27 with a planetary A index of 25. This would match last Sunday’s activity, except March 26 and 28 are expected to have higher geomagnetic activity than March 8 and 10 did, with the planetary A index at 20 on both days. You can read an interesting article about one of the teams in the Air Force Space Weather Squadrons. Over the seven days from March 14-20, they predict a planetary A index of 8, 5, 10, 10, 8, 8 and 5.
Geophysical Institute Prague says to expect unsettled conditions for March 14, quiet conditions on March 15, quiet to unsettled March 16-17 and quiet March 18-20.
While higher geomagnetic activity may degrade HF propagation, especially over paths that cross high latitudes, last weekend's activity brought welcome auroral propagation for VHF operators.
Reader Mail
Paul Kiesel, K7CW, of Tahuya, Washington (grid square CN87), wrote, “I just wanted to let you know that we had a fairly nice radio aurora on 6 meters last night. The Kiruna, Tromso and CARISMA magnetometers, as well as the NOAA POES Satellite, all indicated excellent conditions when I checked them at around 0415 UTC March 9. Sure enough, I heard KE7V [in CN88, Paul’s brother] right away and worked VE7DAY (CO70). VA6AN (DO33), KL7NO (BP54) and VE6TA (DO33) followed soon after. The best DX for us was K1TOL (FN44) at 0533 UTC. This was my best DX buzz-mode contact on 6 meters to date, though I’ve worked Lefty before on auroral-E. There may have been conditions on 2 meters, as well, but when I checked, I heard nothing on that band. This is the best aurora we’ve had in many months. Might be an indicator of good things to come old-sol-wise.”
Note the path from Paul to K1TOL was about 2660 miles, and to KL7NO, about 1955 miles.
I asked Paul to tell us more about buzz-mode (signals bounced off the auroral curtain) vs. auroral-E propagation: “Signals reflected back from the auroral curtain typically are fluttery, distorted and hissy or gravelly sounding. Sometimes SSB signals are hard to understand because the distortion is so bad. Auroral-E signals are clear, just like other sporadic-E signals. The difference is that we know that the aurora is the prop mode function, not the normally ionized E-layer. As far as working K1TOL last night goes, it is unusual to work a station as far away as he is via fluttery aurora. It’s usually auroral-E that will get you the real DX. I’ve worked only one other East Coast station via buzz mode aurora. It was K7BV/1 in Connecticut a couple of years ago. So, our working K1TOL via buzz mode was an unusual occurrence.”
Paul shared with us the magnetometers he mentioned in his first e-mail.
Tromso (Norway): “I check the downward blue trace deviation from horizontal. The lower, the more intense the aurora. Solar wind Bz must be negative. This relates to the Interplanetary Magnetic Field orientation. You can check the current reading on the lower-left side of spaceweather.com. A south-pointing IMF makes the earth vulnerable to solar wind, and corresponds to a negative Bz.”
Kiruna (Sweden): “I check the downward black trace deviation from horizontal. The lower, the more intense the aurora. Solar wind Bz must be negative.”
CARISMA (Canada): “Canadian reading from a north-south line of magnetometers. Gives a decent indication of real-time au conditions over North America.” It shows a green halo when nothing special is going on.
NOAA POES: “This is a good indicator of intensity. POES satellite takes a reading on each orbit, so the presentation represents a reading that may be up to 88 minutes old. The more intense the conditions, the fatter and redder the au oval is presented.”
Finally, Terry McGleish, KC4TM, of North Fort Meyers, Florida, recommends checking 10mbeacons.com for 10 meter beacon spotting reports. You can find details on Terry’s own beacon. He says there was a recent increase in reports beginning March 11.
Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears in The ARRL Letter. Check here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.
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