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The K7RA Solar Update


Sunspots are gone again this week, with none observed since September 12. 

Average daily sunspot number declined to zero this week from 7.6 last week. Average daily solar flux was unchanged at 68.6. Average daily planetary A index declined from 12.6 to 9.7, while average daily mid-latitude A index went from 10 to 8.3.

The Autumnal equinox is this weekend, at 0154 UTC on Sunday, September 23, 2018. The weeks before and after the equinox are typically a better period for worldwide HF propagation because both the Northern and Southern Hemispheres are seeing an equal amount of solar radiation.

For some reason the space weather squadron at USAF has been unable to transmit their daily 45-day forecast of solar flux and planetary A index, so we are relying on a recent 27 day forecast from NOAA.

Unfortunately, unlike the daily Air Force prediction, this one is several days old and only comes out weekly:

Predicted solar flux is 68 on September 21-26, 69 on September 27 through October 1, 70 on October 2-9, and 69 on October 10-13.

Predicted planetary A index is 5 on September 21-22, then 16 and 12 on September 23-24, 5 on September 25-30, 8 and 10 on October 1-2, 5 on October 3-6, then 20, 30, 10, 18, 15 and 8 on October 7-12, and 5 on October 13.

Here is the latest video from Dr. Tamitha Skov:


Mark Lunday, WD4ELG, of Greensboro, North Carolina sent an email titled, “Who says bands are dead?” and a list of stations copied on 15-meter FT8 around 2300 UTC on September 18: UT0LQ (Ukraine), A41CK (Oman), DL1NKS (Eichenbuehl, Germany), OG1AO (Finland), SP0QMP (Poland), W0ITT (Missouri), K3JYD (West Virginia), K4MIA (Florida), CO2RQ (Havana, Cuba) and XE1IM (Michoacan, Mexico). Mark was using a 40-meter dipole antenna hung at 59 feet.

This week’s geomagnetic forecast from OK1HH:

Geomagnetic activity forecast for the period September 21 to October 17, 2018

Geomagnetic field will be:

Quiet on September 26-28, October 4-5, 16-17

Quiet to unsettled on September 21, 25, 30, October 3, 12, 15

Quiet to active on September 24, 29, October 2, 6, 11, 13-14

Unsettled to active on September 23, October 1, 6, 9-10

Active to disturbed on September 22, October 7-8

Solar wind will intensify on September 22-24, (25), 29, October 1-2, 6-9


- Parenthesis means lower probability of activity enhancement.

- Reliability of predictions will be low again.

F. K. Janda, OK1HH

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of numbers used in this bulletin, see

An archive of past propagation bulletins is at More good information and tutorials on propagation are at

Monthly propagation charts between four USA regions and twelve overseas locations are at

Instructions for starting or ending email distribution of ARRL bulletins are at

Sunspot numbers for September 13 through 19, 2018 were 0, 0, 0, 0, 0, 0, and 0, with a mean of 0. 10.7 cm flux was 69.6, 69, 68.5, 69.1, 67.8, 68.1, and 67.9, with a mean of 68.6. Estimated planetary A indices were 17, 16, 8, 6, 11, 6, and 4, with a mean of 9.7. Estimated mid-latitude A indices were 17, 11, 7, 5, 9, 5, and 4, with a mean of 8.3.




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