Solar activity weakened a little or increased slightly over the past week, depending on which measure we choose. The June 11-17 average daily sunspot number declined from 112.4 over the previous seven days to 99.9 during the recent period. Average daily solar flux rose from 131.4 to 135.9 over the same period.
The current outlook from NOAA and USAF has solar flux at 150, 152 and 153 on June 19-21, 148 and 140 on June 22-23, 135 on June 24-25, then 130, 120 and 110 on June 26-28, then 100 and 110 on June 29-30, 115 and 120 on July 1-2, 125 on July 3-4, 120 on July 5-6, 125 on July 7, 130 on July 8-10 and 125 on July 11-12. Flux values then dip below 100 on July 19-24, and rise above 100 after July 26.
All of this looks pretty weak when compared to solar cycles 21-23, but normal for current cycle 24, which peaked in April and May of 2013, then again about 40 points higher in February and March 2014. This is based on a 3-month moving average of Boulder sunspot numbers. For a straight monthly average, we see May 2013 peaking at 125.6 and February 2014 at 174.6.
Since then, numbers have steadily declined, with the weekly sunspot number averages for the last seven weeks at 60.9, 146.9, 92.1, 56.1, 34.3, 112.4 and 99.9. (See https://en.wikipedia.org/wiki/Solar_cycle_24)
Predicted planetary A index is 6 on June 19, 5 on June 20-22, 8 on June 23-24, 6 on June 25, 5 on June 26 through July 4, then 25, 15, 12 on July 5-7, then 10, 5 and 8 on July 8-10, then 15, 12 and 8 on July 11-13.
After this, planetary A index drops to 5, where it remains for the foreseeable future until early August when it rises to 25, indicating a geomagnetic storm. But early August seems a long time from now, and far beyond the short term forecasts we usually examine.
Petr Kolman, OK1MGW, of the Czech Propagation Interest Group sees quiet geomagnetic conditions on June 19-21, quiet to unsettled June 22-25, quiet to active June 26-27, quiet June 28-30, mostly quiet July 1-2, quiet to unsettled July 3, active to disturbed July 4, quiet to active July 5, quiet to unsettled July 6-8, mostly quiet July 9-10, quiet to active July 11-12, quiet to unsettled July 13-14 and mostly quiet July 15.
OK1MGW expects increased solar wind July 4-5 and July 11-12.
At 0456 UTC on June 19 the Australian Space Forecast Centre issued a geomagnetic disturbance warning, saying increased geomagnetic activity is expected due to a coronal mass ejection on June 21-22.
“A coronal mass ejection has been observed in association with a flare from region 2371 at 1736 UTC on June 18. The majority of the CME material appears primarily directed to the NE of the sun, however further analysis suggests that the Earth will be impacted by the edge of the CME around 09UT on June 21. Minor storm periods are expected following the impact with major storm levels possible at high latitudes.”
June 21: Active to Minor Storm, with major storm periods possible at high latitudes.
June 22: Mostly unsettled to active with minor storm periods possible at high latitudes.
Spaceweather.com also reported the possibility of M-class flares on June 19, from sunspot region 2371, which is pointing toward Earth.
David Moore sent a link to an article about a new solar storm prediction tool.
Rich Zwirko, K1HTV, sent a six meter report.
“The Mid-Atlantic experienced some, but not much Es during this year’s June ARRL VHF Contest. The only DX worked to the east was EA8DBM in the Canary Islands and VP9/WA4PGM, much closer in Bermuda. I managed to work a number of Caribbean stations with C6ATA having the most consistent signal. The first of two surprises occurred when I snagged Dave, KM3T/R while he was roving in the rare FN51 grid on Cape Cod, MA. The second surprise and the only double hop QSO to the west occurred with only 2 minutes left in the contest when I worked N6AMJ in DM14.
“On June 16, around 1:30 PM local time, the first 6 Meter DX opening from the K1HTV Virginia QTH to Eastern Europe occurred. I worked HA5LI for Gyuri’s first 6 Meter QSO with a U.S. station this year. This was followed a few minutes later when I worked S59A. CT1HZE was again into North America for hours, working as far west as Missouri and Oklahoma. Joe’s QTH on the southwestern coast of Portugal sure helps. 4X4DK was briefly heard, but not long enough or loud enough for a QSO.
“Some nice signals double hopped from Arizona and New Mexico later that same afternoon. After a very slow start, it looks like the 2015 Es season is starting to ramp up.”
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 athttp://arrl.org/w1aw-bulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us/.
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 http://arrl.org/propagation.
Instructions for starting or ending email distribution of ARRL bulletins are athttp://arrl.org/bulletins.
Sunspot numbers for June 11 through 17 were 101, 96, 97, 117, 107, 87, and 94, with a mean of 99.9. 10.7 cm flux was 139.9, 136.7, 136.1, 131.7, 134.8, 136.1, and 135.8, with a mean of 135.9. Estimated planetary A indices were 9, 7, 10, 20, 14, 11, and 14, with a mean of 12.1. Estimated mid-latitude A indices were 9, 8, 10, 19, 13, 10, and 14, with a mean of 11.9.
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