SB PROP @ ARL $ARLP028 ARLP028 Propagation de K7RA
ZCZC AP29 QST de W1AW Propagation Forecast Bulletin 28 ARLP028 From Tad Cook, K7RA Seattle, WA July 13, 2012 To all radio amateurs SB PROP ARL ARLP028 ARLP028 Propagation de K7RA
Solar activity rose moderately this week. Average daily sunspot numbers were up nearly 3 points to 120.9, and average daily solar flux rose over 28 points to 166.8. There was quite a bit of geomagnetic activity, the most happening on July 9, when the mid-latitude A index reached 29, planetary A index was 30, and Alaska's college A index was 60. That day I stopped in to visit K7SS on my way back from a trip to Oregon, and a check of the bands showed HF conditions were quite difficult.
Sunspot group 1520 was directly facing Earth on July 12 at 1653 UTC when it spewed out an X.14 class solar flare. We've seen flares off to one side or another that had limited effect, but this one was aimed straight at us. There was an immediate SID (Sudden Ionospheric Disturbance) event, and the resulting CME should reach Earth some time around 1020 UTC Saturday, July 14. This could be bad news for operators in the IARU HF World Championship and other operating events this weekend. The accuracy of the 1020 UTC impact estimate is plus or minus 7 hours. The 24-hour contest begins at 1200 UTC Saturday. See
http://www.arrl.org/iaru-hf-championship/for details.
The latest prediction shows planetary A index at 8, 18 and 15 on July 13-15, then 5 on July 16-26, then 20 on July 27-29, 10 on July 30-31, 15 on August 1-2, 10 on August 3-4, 8 on August 5, and 5 on August 6-22.
Predicted solar flux is 165 on July 13-15, then 160, 145, 130, and 120, on July 16-19, 105 on July 20-21, then 115, 120, 130, 140, 145 and 150 on July 22-27, and 165 on July 28 through August 2, 160 on August 3-4, then 165, 155, and 150 on August 5-7, and 145 on August 8-10.
If you check
http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html and compare the July 11 and July 12 predictions, you can see a big difference between the forecast in this bulletin (July 12) and the one presented in this week's ARRL Letter, based on the July 11 projection.
Over the past week, four new sunspot groups appeared. On July 7, group 1520 was new and on July 8, older group 1517 (visible since July 1) disappeared. On July 9 group 1513 (visible since June 26) was gone and 1521 was new. On July 10, group 1515 (visible since June 27) disappeared, and on July 11 group 1518 (around since July 4) was gone. On June 12, two new groups, 1522 and 1523 appeared.
Petr Kolman, OK1MGW, again provides us with the Czech Propagation Interest Group geomagnetic activity forecast. Expect unsettled to active conditions on July 13-15, mostly quiet July 16-18, quiet to unsettled July 19-21.
You can follow progress of any geomagnetic disturbance this weekend by checking
http://spaceweather.com/ and
http://www.spaceweatherlive.com/en. Note the last site is available in Dutch, French and German by selecting your language of choice in the drop-down on upper right.
We received even more email about the old BC-458 SSB conversion, including some corrections to the correction in the last bulletin. We won't cover the subject any longer in this bulletin, but the original March 1956 QST article by W2EWL is a treat to look at. If you are an ARRL member, you can find it in the QST archive by logging into your account at
http://www.arrl.org/ and then going to
http://www.arrl.org/arrl-periodicals-archive-search. Just enter "W2EWL" in the Author Call field, and March 1956 for the month and year. There you can download a 1.6 MB pdf of the article.
Walt Knodle, W7VS of Bend, Oregon sent along an article titled "MRI of the Sun's Interior Motions Challenges Existing Explanations for Sunspots". Read it at
http://www.sciencedaily.com/releases/2012/07/120709092457.htm.
You can read articles about the most recent solar flare at
http://www.livescience.com/21573-major-solar-flare-erupts-giant-sunspot.html and
http://www.space.com/16557-giant-sunspot-ar1520-solar-flares.html.
Jon Jones, N0JK sent a message about the big recent 6 meter opening and notes it was June 29, not June 30. He says, "In Kansas, we were at the edge of it. N0LL worked MM0AMW at 1219 UTC followed by LA7HJA at 1545 UTC. I logged JW7QIA at 1642 UTC. I was running 100 w and a 2 element Yagi portable for the contact with Peter. He was using a stack of two 5 el Yagis. I heard him for about 5 minutes. The VE4SPT/b EO26 was 599 at the same time."
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 of past propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation. Find more good information and tutorials on propagation at
http://myplace.frontier.com/~k9la/.
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 July 5 through 11 were 122, 131, 127, 113, 137, 122, and 94, with a mean of 120.9. 10.7 cm flux was 164.6, 157.7, 158.4, 177.7, 173.8, 173.4 and 161.7, with a mean of 166.8. Estimated planetary A indices were 14, 16, 8, 13 30, 13, and 10, with a mean of 14.9. Estimated mid-latitude A indices were 13, 14, 8, 15, 29, 15, and 10, with a mean of 14.9. NNNN /EX
