Propagation de K7RA
27 August, 2011
ARLP034
Solar activity rose this week, with the average daily sunspot number increasing over 40 points to 66, and average daily solar flux up over 13 points to 101.9.
Predicted solar flux for August 26 is 110, and 115 for August 27-28, 110 for August 29 to September 1, 105 for September 2-3, 100 for September 4-5, 95 on September 6-7, and bottoming out at 90 on September 8-12. The next peak of activity is predicted for September 22-23.
Predicted planetary A index is 5 for August 26-27, 10 on August 28, 8 on August 29, and 5 on August 30 through September 2, then 8 on September 3, 10 on September 4-6, 7 on September 7, and 5 on September 8-10.
Geophysical Institute Prague predicts quiet conditions for August 26, unsettled on August 27-28, quiet to unsettled August 29 and quiet conditions on August 30 through September 1.
A story forwarded from a British newspaper by a reader warned that "a huge mass of electrically charged particles thrown out by a giant eruption on the Sun is due to strike the earth tonight." But the article itself is undated, and the web page continuously updates to show the current date. The link to the article was sent to me on August 21, but the event didn't happen then, and is not happening now, nor is such an event predicted for the next few days. Down the left margin of the page are ads for astrologers, and on the right margin are links to over 80 stories about celebrity gossip.
If you do a web search for phrases from the article - which is at
http://www.dailymail.co.uk/news/article-200952/
power-cuts-threat-sun-storm-hits-earth.html - you find it quoted all over the net by people assuming that this is about to happen, some of them quite alarmed. But looking at the latest prediction from NOAA/USAF at http://www.swpc.noaa.gov/
ftpmenu/forecasts/45DF.html shows no predicted rise in the A index, which would be large if such an event were predicted.
So what date was the article published? I doubt if this newspaper has had a science editor for a number of years, so perhaps they keep running the same article with its dire warnings, and only the celebrity gossip changes.
The key to the date of this article lies in searching the newspaper archive for the headline. If you enter a portion of the headline into the search box next to the article, the actual date is revealed: October 29, 2003. This is nearly eight years ago. Now we know why nobody predicted this event. In these fast moving times, 2003 might seem to some like ancient history.
Try doing a web search of a phrase from this article. Some of the results are quite funny. You will see it referenced all over the web as if it just happened and were breaking news.
Last week's bulletin mentioned the new issue of WorldRadio expected last Saturday, which would have an updated propagation column by K9LA. The new September issue didn't actually appear online until several days later. You can read it now at http://www.worldradiomagazine.com.
The propagation column by K9LA, Carl Luetzelschwab pays tribute to the late Bob Brown, NM7M and his writings about propagation for the amateur community. Carl mentions that one of Bob's popular books is available for download from Carl's web site. Just go to http://myplace.frontier.com/~k9la/ and click on General on the left side of the page, then right-click the link for "Little Pistol's Guide to HF Propagation" to download the PDF.
We are just a few weeks away from the Autumnal Equinox, a time when we see better HF propagation than we did during the summer. You can check the effect of seasonal change by running two instances of a propagation program, and switching back and forth to see the same projection over two different dates.
You can download W6ELprop from http://www.qsl.net/w6elprop/ and try what I did, which was to compare August 2 with September 22. The predicted smoothed sunspot number for August was 59, and for September it is 62. You could use those numbers, or use the same sunspot number on both projections to isolate the seasonal effect.
I ran my projection between Atlanta, Georgia and England. You bring up Atlanta coordinates in W6ELprop by entering the prefix W4, and England with the G prefix. You can see the generally improved signal strengths and longer openings in the September prediction.
If you want the latest smoothed sunspot numbers for this month and off into the future, go to http://www.swpc.noaa.gov/
weekly/pdf/prf1875.pdf and look at the table on page 18. Every 4-5 issues they have an updated projection for the current solar cycle.
Finally, do you think Cycle 24 is weaker and still progressing slower than previous solar cycles? You are correct. For a comparison of Cycles 21, 22, 23 and 24, check
http://www.solen.info/solar/cyclcomp.html.
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 at
http://arrl.org/propagation-of-rf-signals.
For an explanation of the numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere.
An archive ofpast propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation.
Find more good information and tutorials on propagation at
http://mysite.ncnetwork.net/k9la/index.html.
The multiple websites mentioned in this bulletin can be found in packet and internet versions of Propagation Forecast Bulletin ARLP033.
Monthly propagation charts between four USA regions and twelve
overseas locations are at http://arrl.org/propagation.
Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins.
Sunspot numbers for August 18 through 24 were 53, 46, 59, 66, 82, 81, and 75, with a mean of 66. 10.7 cm flux was 97.8, 98.2, 100.5, 100.9, 108.2, 103.7, and 104.1, with a mean of 101.9. Estimated planetary A indices were 3, 2, 5, 3, 7, 9, and 6, with a mean of 5. Estimated mid-latitude A indices were 1, 1, 4, 3, 5, 8, and 5, with a mean of 3.9.
Source: The American Radio Relay League
• All propagation reports can be found at:
http://www.southgatearc.org/propagation
|
