This week the average daily sunspot number dropped 36 points to 56.1, and average daily solar flux was down 25.7 points to 97.6. Geomagnetic numbers indicated more stability than the previous week (May 14-20) with average daily planetary A index declining from 10 to 4.4, and mid-latitude A index down from 9.7 to 5.

The latest forecast from NOAA/USAF has solar flux at 90, 95, 100, 105 and 110 on May 29 through June 2, 115 on June 3-4, 125 and 120 on June 5-6, 115 on June 7-10, 110 and 105 on June 11-12, 100 on June 13-14, 95 on June 15, 90 on June 16-17, 95 on June 18-20, 100 on June 21-23 and 95, 90, 105, 110 and 115 on June 24-28, and 120 on June 29-30. Flux values then peak at only 125 on July 1-2, before dropping back below 100 on July 12.

Planetary A index is predicted at 12 and 8 on May 29-30, then 5 on May 31 through June 6, then 10, 25 and 20 on June 7-9, 12, 8 and 5 on June 10-12, then 8, 15 and 12 on June 13-15, 5 on June 16-23, then 8, 12 and 8 on June 24-26 and 5 on June 27-28.

F.K. Janda, OK1HH, predicts the geomagnetic field will be quiet to unsettled May 29, mostly quiet May 30, quiet to unsettled May 31, mostly quiet June 1, active to disturbed June 2, quiet to active June 3, mostly quiet June 4-5, quiet to unsettled June 6, quiet to active June 7-9, disturbed on June 10-11, mostly quite June 12, quiet June 13, quiet to active June 14, active to disturbed June 15, quiet to active June 16 and quiet on June 17.

Howard Lester, N7SO, of Schuylerville, New York (FN33eb) wrote on May 28, “I got on the radio last evening to see if there was any E2 on 6 meters. The band was dead at 2330 UT, but I left it on 50.125 to monitor. At 0005 UT I heard a K0 from Missouri calling CQ, coming in loud at S5, so I jumped off the sofa and we had a nice little chat for a couple of minutes. After, I heard him work a VA3. My antenna is a little triangular loop up 15 feet.”

Last week David Moore sent a couple of links to articles about observations from the NASA Solar Dynamics Observatory. See them here:

http://www.nasa.gov/image-feature/solar-dynamics-observatory-sees-cinco-de-mayo-solar-flare

http://www.nasa.gov/image-feature/coronal-loops-over-a-sunspot-group


On May 22, Bob Kupps, HS0ZIA, of Chiang Mai, Thailand wrote, “We had a very nice 15-meter opening last night May 21 from around 1430-1530 UTC (2130-2230 local time) right over the North Pole into almost all of North America from New Brunswick to Arizona. Using a K3 at 100 W to a 5/5 Optibeam stack at 15 and 30 meters elevation. Fun!”

Check out Bob’s antennas on his QRZ.com page. Quite a stack!

Don’t forget the CQ World Wide WPX CW Contest this weekend. Look here for more info: http://www.cqwpx.com/


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. More good information and tutorials on propagation are at http://k9la.us/.

Archives of the NOAA/USAF daily 45 day forecast for solar flux and planetary A index are in downloadable spreadsheet format at http://bit.ly/1IBXtnG and http://bit.ly/1KQGbRm.

Click on “Download this file” to download the archive and ignore the security warning about the file format.

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 May 21 through 27 were 36, 81, 69, 74, 63, 46, and 24, with a mean of 56.1. 10.7 cm flux was 101.8, 99.1, 97.7, 98.7, 96.5, 94.5, and 95.2, with a mean of 97.6. Estimated planetary A indices were 3, 3, 4, 5, 4, 6, and 6, with a mean of 4.4. Estimated mid-latitude A indices were 5, 4, 5, 6, 3, 6, and 6, with a mean of 5.