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SEATTLE, WA, Jul 7, 2006--Solar activity was up this week. Average daily sunspot numbers rose nearly 22 points to 35.6 from last week. Average solar flux rose as well by 11 points -- from 75.7 to 86.7. The moderately active geomagnetic day this week was July 5, with a planetary A index of 19, and the college A index from the magnetometer near Fairbanks at 28.
The increased geomagnetic activity was due to a high-speed solar wind stream from a coronal hole on the sun beginning July 4. Earth was vulnerable, due to a south-pointing interplanetary magnetic field (IMF). When the IMF points north, Earth is less vulnerable. The IMF is again pointing south on July 7. The next increase in geomagnetic activity is predicted for July 9. The current prediction for the planetary A index for July 7-10 is 8, 10, 25 and 18. Solar flux for those days is predicted at about 85.
When the solar wind stream hit earlier this week, a radio burst from giant sunspot 898 was recorded July 5 at 1743 UTC by Thomas Ashcraft of Lamy, New Mexico. He used receivers tuned just above 17 meters and just above 15 meters to produce a binaural audio recording -- best appreciated with stereo headphones (thanks to Don Mayhall, N5DM for the tip).
We received more notes on 6 meters and Field Day. Bill Baker, W5GT, reports his club entry from W5NOR in Oklahoma used a rotatable dipole on 6 meters and made 109 contacts during Field Day weekend, June 24-25.
Bill Van Alstyne, W5WVO, of Rio Rancho, New Mexico, wrote of his FD 2006 experiences on 6 meters:
"Saturday evening saw some really nice double-hop into the east (NY, PA, MD, VA mostly), plus the usual single-hop path to the mid-way point (MO, IA, IL). Signal strength on the East Coast stations was very good, in some cases as good as the Midwest stations. Worked a new grid square (FM09) in the WV panhandle, a club FD effort that decided to activate this somewhat-rare grid as well as work the contest. Sunday morning featured a long, strong, and fairly broad opening into the Midwest -- MO, IA, IL, IN. WI, MN, and others. Only sporadic East Coast contacts, mostly in FL."
Bill is looking forward to the CQ World Wide VHF Contest July 15-16.
Eric Hall, K9GY, of Lansing, Illinois, reminds us to operate the IARU contest this weekend and specifically to work the competing teams in World Radiosport Team Championship 2006 (WRTC-2006), taking place in Brazil. You can follow the progress of the teams via an online "Scoreboard."
WRTC-2006 Propagation: Best Bets
Propagation to South America from the Northern Hemisphere should be good this weekend. From California, best times should be on 80 meters around 0330 UTC and 0530-0900 UTC, 40 meters 0330-1000 UTC, 20 meters 0100-0700 UTC, and 15 meters 1700 UTC-0530 UTC, with the best bet around 2330-0430 UTC. Although not a sure bet, check for 10-meter openings 2000-0500 UTC.
From Chicago, 80 meters looks best 0330-0900 UTC, 40 meters 0130-0930 UTC, and 20 meters 2230-0530 UTC. Fifteen meters does not look promising, but your best bet is 2100-0400 UTC.
From Dallas, 80 meters looks good 0230-0930 UTC, 40 meters 0100-1000 UTC, 20 meters 2230-0530 UTC, 15 meters 1700-0200 UTC, and perhaps 10 meters, best chances 1800-0400 UTC, with stronger signals toward the end of that period.
From Philadelphia, 80 meters looks good 0200-0830 UTC, 40 meters 0000-0730 UTC, 20 meters 2200-0530 UTC, and perhaps 15 meters from 2100-0300 UTC.
You can work out paths from your own location using the method outlined in an earlier propagation bulletin.
Of course, for the IARU contest, you work stations all over the world, not just in Brazil. The IARU HF World Championship rules are on the ARRL Web site.
Second Quarter Review
The end of June brings to a close the second quarter of 2006. This is a good time to review average quarterly and monthly sunspot and solar flux numbers. It's a good way to spot trends.
From the first quarter of 2003 through the second quarter of 2006, the average daily sunspot number was 120.3, 107.3, 110.2, 99.2, 72.9, 71.3, 69.3, 61, 46.1, 55.7, 58, 36, 18.1 and 39.7.
The average daily solar flux for the same period was 134.3, 124.2, 120.8, 137.4, 111.1, 99.5, 111, 104.8, 96.4, 93.1, 93.6, 84.5, 78.5 and 82.1.
Three-month averages should be a bit smoother than one-month averages, and from the numbers above you might think we'd already hit bottom on the solar cycle and begun a rebound. Although activity is low, we haven't seen the weeks of zero sunspots that we experienced about a decade ago during the last solar minimum. Also, look at the monthly numbers below. Although there was a slight uptick in sunspot numbers and solar flux for the last quarter, the monthly numbers for the three months that make up this last quarter show an orderly decline.
The average daily sunspot numbers for the months May 2005 through June 2006 were 65.4, 59.8, 68.7, 65.6, 39.2, 13, 32.2, 62.6, 26.7, 5.3, 21.3, 55.2, 39.6 and 24.4. Average daily solar flux for the same months was 99.5 , 93.7, 96.5, 92.4, 91.9, 76.6, 86.3, 90.8, 83.4, 76.5, 75.5, 88.9, 80.9 and 76.5.
Solar Minimum Forecast
We have a new forecast from NOAA Space Environment Center for the bottom of this solar cycle. Compared to the forecast of the past few years, it puts the bottom of the cycle just slightly farther out than the forecast of a few years ago -- which is all we had until this week.
You can see it in the charts in the back of the July 4 Preliminary Report and Forecast. Note on pages 9 and 10 that the table of predicted smoothed sunspot numbers put the minimum in January 2007. It may be more realistic to characterize it as occurring between December 2006 and May 2007, however. The projection running just one week earlier is the same one that has been out for several years. Note the minimum sunspot numbers at December 2006 and January 2007. Similar numbers for the smoothed solar flux in last week's table showed a minimum from December 2006 through April 2007, while this week's forecast shows it running from January through April 2007. Not much difference, but a slight shift out into 2007, and the first update to this forecast in years.
For More Information
For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page and the article "The Sun, the Earth, the Ionosphere: What the Numbers Mean, and Propagation Predictions," by Carl Luetzelschwab, K9LA. An archive of past bulletins is on the ARRL Web site.
Weekly Sunspot Numbers
Sunspot numbers for June 29 through July 5 were 35, 38, 36, 34, 38, 40 and 28, with a mean of 35.6. 10.7 cm flux was 85.5, 86.1, 85.5, 87.1, 85.9, 92, and 84.7, with a mean of 86.7. Estimated planetary A indices were 12, 8, 5, 2, 4, 13 and 19, with a mean of 9. Estimated mid-latitude A indices were 8, 7, 3, 1, 2, 11 and 18, with a mean of 7.1.
Amateur solar observer Tad Cook, K7RA, 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. Readers may contact the author via e-mail.
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