Solar activity was down this week (September 18-24) when compared with a week earlier, but solar flux is on a rising trend.

Average daily sunspot numbers dropped from 124.9 (for September 11-17) to 80.9, and average daily solar flux slipped from 139.8 to 128.3.

The latest predicted solar flux and planetary A index has flux values at 165 on September 26-28, 170 on September 29-30, 165 and 160 on October 1-2, 155 on October 3-4, 150 on October 5-7, 145 on October 8-9, 140 on October 10-11, then 135 and 130 on October 12-13, 125 on October 14-15, and 120 on October 16-18. Flux values are then expected to rise to 155 on October 30-31.

Predicted planetary A index is 15 on September 26, 12 on September 27, 15 on September 28-29, 10 on September 30, 8 on October 1-2, 5 on October 3-14, then 8, 15 and 8 on October 15-17, 5 on October 18-19, 8 on October 20-21, 12 on October 22, and 15 on October 23-24.

Petr Kolman, OK1MGW, makes geomagnetic predictions, and believes the geomagnetic field will be quiet to active September 26-27, quiet to active September 28 through October 3, mostly quiet October 4-7, quiet to unsettled October 8-9, quiet October 10-12, mostly quiet October 13, quiet to active October 14-15, mostly quiet October 16-17, quiet to unsettled October 18-20, and quiet to active on October 21-22.

Earth’s geomagnetic field has been unsettled recently, with planetary A index at 25 on September 24 and College A index (high latitude) at 57. Spaceweather.com reports this is not due to a CME or solar flare, but a crack in the Earth’s magnetosphere, opening a spot for the solar wind to pour in.

John Campbell, K4NFE, of Huntsville, Alabama sent in an article and video explaining the difference between solar flares and Coronal Mass Ejections.

Read it at http://www.universetoday.com/114729/nasa-explains-the-difference-between-cmes-and-solar-flares/

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 September 18 through 24 were 75, 91, 75, 72, 87, 90, and 76, with a mean of 80.9. 10.7 cm flux was 120, 122, 119, 124, 130, 138, and 145, with a mean of 128.3. Estimated planetary A indices were 8, 22, 6, 7, 9, 11, and 25, with a mean of 12.6. Estimated mid-latitude A indices were 7, 23, 4, 7, 9, 9, and 19, with a mean of 11.1.