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![Previous (earlier) Story](/images/sty-down.gif "Fall Launch Viewed for "SuitSat" as ARISS-US Delivers Hardware"){kind=small} Previous: Fall Launch Viewed for "SuitSat" as ARISS-US Delivers Hardware |  Next: US Senate Version of Amateur Radio Spectrum Protection Act of 2005 Introduced |
SEATTLE, WA, Jun 17, 2005--If you look at the average of daily sunspot or solar flux numbers for the past week, you'll see hardly a change from the previous period. This does not mean there was no activity or zero sunspots, but the average daily solar flux is exactly the same the past week as the one previous, and the average daily sunspot number was down by less than one point. Sunspot counts rose in the earlier period, peaked at the end of that reporting week (Thursday through Wednesday) and declined over the next seven days. Last Friday, June 10, sunspots 775 and 776 were transiting the center of the visible solar disk, which meant they were in the best position for affecting Earth.
A coronal mass ejection (CME) on June 9 caused a geomagnetic storm on June 12, when the arrival of the ejection and solar wind was met with a south-pointing interplanetary magnetic field. When the field points north, it helps protect the Earth from the effects of solar wind. But when it points south, Earth is vulnerable. On June 13 the field again pointed north.
Currently we are experiencing effects from a CME that swept over Earth around 0900 UTC on June 16. This was a weak disturbance, but it was followed by a moderate solar wind. Expected planetary A index, a measure of geomagnetic stability worldwide, is expected around 25, 15, 10 and 8 for June 17-20. Solar flux is expected to remain below 100 until the end of this month.
Currently there is a large sunspot detectable on the far side of the sun. A large sunspot, number 779, which only emerged this week is currently at the center of the visible solar disk, directly facing Earth.
Now let's look at ARRL Field Day, a very popular activity that generates a great deal of interest and mail this time of year. The dates are Saturday and Sunday, June 25-26, and recurring coronal holes and a high-speed solar wind are expected to result in active to minor storm levels around June 24-27. It is difficult to predict with real accuracy this far out, but according to the U.S. Air Force the expected planetary A index for June 24-27 is 15, 20, 20 and 15. Solar flux around that weekend is expected around 85-90. By the way, I found an interesting article, "Air Force Space Weather Troops," about a solar observatory the Air Force operates in Puerto Rico.
Next week we'll revisit Field Day in the hours leading up to next weekend. Meanwhile, this weekend in addition to other activities is the All Asian DX CW Contest, SMIRK 6-meter Contest, and the Kid's Day operating event. Next week is also the summer solstice--the "longest day of the year" in the Northern Hemisphere--June 21. This day gets really long the farther north one moves in the Northern Hemisphere. For instance, on June 21 in Los Angeles the sun will rise at 5:50 AM and set at 8:01 PM--a 14 hour, 11 minute period. But in Seattle, the sun rises 29 minutes earlier at 5:21 AM and sets a whole hour later than in LA, at 9:01 PM--a 15 hour, 41 minute period from sunrise to sunset.
Eric Hall, K9GY, reports he was operating mobile Saturday, June 11 (the weekend of the ARRL June VHF QSO Party) from FM08rp at 3500 feet elevation west of Shenandoah National Park in northeastern Virginia. With just a 6-meter whip on his car, he copied (and believes he "almost worked") VP5/N4VHF in FL31. He did snag stations in FN11, FN20, FN21, FN00, FN01, FN30, FN31, FN32 and EM96.
By the way, to locate these and other grid squares, check AMSAT's Grid Square Conversion site. It will provide latitude/longitude coordinates for any grid square, and it also works with the more precise six-character locators. Running it to find grid square from map coordinates, I discovered my six-character locator is CN87uq.
For more information concerning radio propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page. An archive of past bulletins is available on this Web site.
Sunspot numbers for June 9 through 15 were 99, 103, 85, 85, 73, 44 and 64 with a mean of 79. 10.7 cm flux was 116.1, 114.3, 108, 103, 91.8, 93.8 and 94.5, with a mean of 103.1. Estimated planetary A indices were 5, 5, 6, 35, 33, 10 and 21 with a mean of 16.4. Estimated mid-latitude A indices were 3, 2, 6, 23, 17, 8 and 14, with a mean of 10.4.
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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