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The K7RA Solar Update


Average daily sunspot numbers dropped from 109.1 on July 2-8 to 73.7 in the past week, July 9-15. Average daily solar flux dropped from 123.2 to 114.8 over the same two periods. Geomagnetic indices were more active, with average daily planetary A index increasing from 10 to 13.7, and average mid-latitude A index going from 8.9 to 12.3.

The geomagnetic field was active on July 11 when the mid-latitude A index, the high latitude college A index, and planetary A index were 20, 44 and 23. Activity was greater on July 13 when the three indices were 22, 45 and 32.

The July 11 activity was a G1 class geomagnetic storm caused by a high-speed solar wind stream, and similar events caused the July 13 activity. Currently there is very little chance of solar flares or geomagnetic storms over the next few days.

Predicted planetary A index is 8 on July 17-18, 10 on July 19-20, 5 on July 21-30, 18 on July 31, 25 on August 1, and 12 on August 2. On August 3-5 the planetary A index is predicted at 5, then 20 and 25 on August 6-7, and 8 on August 8-10. On August 11 and beyond the planetary A index prediction is 5.

Predicted solar flux is 100 on July 17-19, 95 on July 20-21, 100 on July 22-23, 105 on July 24, 110 on July 25, 115 on July 26, 120 on July 27-31, and 115 on August 1-4. Solar flux is expected to rise to 120 again after August 22.

Recently there have been only a few new sunspot groups, one each on July 7, 8, 10 and 12 and two on July 16.

F.K. Janda, OK1HH, predicts the geomagnetic field will be quiet to unsettled July 17-18, quiet to active July 19, quiet to unsettled July 20-21, quiet to active July 22, mostly quiet July 23-24, quiet July 25-26, mostly quiet July 27, quiet July 28-29, quiet to active July 30, active to disturbed July 31 through August 1, quiet to active August 2, mostly quiet August 3, quiet August 4, mostly quiet August 5, quiet to active August 6, quiet to unsettled August 7, active to disturbed August 8, quiet to unsettled August 9, and mostly quiet August 10-11.

OK1HH expects increases in solar wind on July 19-26, August 1-5, August 8 and August 9-10. He believes there is a lower probability of geomagnetic activity increases on July 19, July 26, August 1-5, and August 8.

David Moore sent a link to an article about combined images from several solar telescopes at .

Scott Bidstrup, TI3/W7RI, sends this report from Costa Rica:

“Propagation here in the low latitudes seems to be starting to settle into its declining solar-cycle funk. Ten and 12 meter openings are becoming less common, and 15 through 20 meter signals seem to be rather lackadaisical, too. The only bright spot for us is that the mid-day blackout is less intense, with signals no longer fading out completely around noon as we are used to, though they are weak. Rare are the days that the bands seem to be really lively with strong signals. It would all be rather depressing, were it not for the improving DX conditions on 80 meters and 40 meters. Even during the peak of the northern summer, our noisiest time of the year here, we're occasionally getting gray-line conditions that enable VKs, ZLs YBs and occasionally JAs to be worked here on 80, in spite of the high noise levels. Jay, HP3AK, reports that this is the noisiest midyear season he can remember here, yet he has nevertheless had some success working the western Pacific on 75 meters. But he has been spending much of his time on 40 meters just to hear signals strong enough to make it over the noise. He recently installed a Waller Flag antenna, and that has helped significantly on both bands, he reports, but it is still no panacea.

“I have seen some references in the literature to the rising altitude of the tropopause in the tropics due to global warming, resulting in more powerful thunderstorms with higher cloud-tops – and therefore possibly more powerful lightning. That, possibly along with El Niño, could account for the increasing 80/40 meter noise levels here this year, especially on 40 meters, which is now approaching the noise levels normally seen only on 80 meters. On the worst days, they have exceeded S9 +40dB, even on 40 meters! As I write this at 5 PM, the noise level on 80 meters is currently S9 +10 and on 40 is about the same. I can't recall noise levels that high here on 40 in the past. Fortunately, they drop fast shortly after sunrise, and don't return until about an hour before sunset, giving us a bit of a break early morning and late afternoon when propagation is still possible through the D layer.

“The fellas bemoaning the crummy Es season on 6 meters in the States are hardly alone; it's been just as anemic here, even more so. Normally by now, our TEP season into South America would be well underway and we'd have enjoyed several Es openings into the Windward Islands and northern South America, but not so this year. We haven't had a single TEP opening yet, and we've had a few weak and short Es openings here, one into KP4, the others into YV, but nothing to write home about, and no DX worth coming running into the shack for. Nothing into the States either, other than a single contact into Florida reported to me by Michael, TI5XP. In the last month, I've only gotten a single 6 meter contact in my log, and that was with a YV I'd already worked many times before. It's been a heck of a DX drought and we're getting desperate!”

Scott mentioned the Waller Flag, which is a low band receiving antenna that has good noise rejection. See,,, and

Thanks to the ARRL Contest Update for this piece on 6 meter propagation:

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of the numbers used in this bulletin, see An archive of past propagation bulletins is at More good information and tutorials on propagation are at

Archives of the NOAA/USAF daily 45 day forecast for solar flux and planetary A index are in downloadable spreadsheet format at and

Click on “Download this file” to download the archive and ignore the security warning about file format. Pop-up blockers may suppress download. I’ve had better luck with Firefox than IE.

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 July 9 through 15 were 120, 124, 91, 59, 44, 39, and 39, with a mean of 73.7. 10.7 cm flux was 121.9, 129, 120.2, 116, 110.1, 105.2, and 101, with a mean of 114.8. Estimated planetary A indices were 6, 10, 23, 11, 32, 7, and 7, with a mean of 13.7. Estimated mid-latitude A indices were 7, 11, 20, 12, 22, 8, and 6, with a mean of 12.3.




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