Average daily sunspot numbers declined over 32 points this week to 39.6.  Average daily solar flux was down more than 8 points to 99.2. Tuesday’s solar flux at 89.5 was the lowest since June 22-25 of last year, when values ranged from 84 to 88.6. Likewise, Tuesday’s sunspot number of 14 was also the lowest since June 25, 2012 when the sunspot number was also 14. Since then both numbers have been recovering, with Wednesday and Thursday’s sunspot numbers at 27 and 45, and solar flux at 93.3 and 98.9.

The latest prediction has solar flux at 105 on June 14-17, 100 on June 18-19, 105 and 110 on June 20-21, 115 on June 22-24, 110 on June 25, 105 on June 26-28, and 110 on June 29 through July 4.  Solar flux is expected to reach a minimum of 95 around July 7-8 and another peak at 115 on July 18-21. Note that ARRL Field Day is June 22-23, right when solar flux is expected to be highest.

Predicted planetary A index is 5 on June 14-16, 8 on June 17-18, 5 on June 19-20, then 25, 18, 10 and 8 on June 21-24, 5 on June 25-27, then 30, 20, 10 and 8 on June 28 through July 1, 5 on July 2-4, 10 on July 5-6, 8 on July 7, and 5 on July 8 through mid-month.

A geomagnetic forecast comes to us this week from Petr Kolman, OK1MGW, who sees quiet to unsettled conditions June 14, mostly quiet June 15-18, quiet to unsettled June 19-20, quiet to active June 21-23, quiet to unsettled June 24, quiet June 25-26, quiet to active June 27, active to disturbed June 28-29, quiet to unsettled June 30 through July 2, quiet to active July 3-4, mostly quiet July 5-6.

Word has come that the link to the W6ELprop installation file at http://www.qsl.net/w6elprop/ is broken. Until it is restored you can find it at ftp://150.214.111.198/pub/ham/propag/W6ELPropInst270.EXE. Unfamiliar with FTP? FTP is File Transfer Protocol, and you can paste that link into your web browser URL window, hit Enter, and a download dialog should appear. W6ELprop works only on Windows computers, and with it you can predict propagation from your station to anywhere else, on any frequency between 3-30 MHz. If you have any trouble installing, try right-clicking the file and running as administrator.

The latest NASA prediction for cycle 24 moves the sunspot peak back to summer 2013, but NOAA predicts the peak for the end of this year. Check pages 16 and 17 at http://www.swpc.noaa.gov/weekly/pdf/prf1970.pdf and note the highest smoothed sunspot and solar flux numbers are predicted in November and December 2013. These are smoothed international sunspot numbers, with a scale quite a bit lower than the Boulder numbers reported here.


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/.

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 June 6 through 12 were 71, 76, 27, 41, 21, 14, and 27, with a mean of 39.6. 10.7 cm flux was 109, 109.8, 103.2, 96, 93.3, 89.5, and 93.3, with a mean of 99.2. Estimated planetary A indices were 17, 32, 10, 9, 13, 6, and 5, with a mean of 13.1. Estimated mid-latitude A indices were 16, 26, 9, 8, 12, 6, and 5, with a mean of 11.7.