Solar activity markedly increased this week, with the sunspot number rising to 130 on Monday, August 1 -- the highest since a reading of 131 on April 14, 2011. The average daily sunspot numbers more than doubled this week compared to last, rising nearly 54 points to 99.3. Sunspot numbers for July 28-August 3 were 84, 88, 101, 128, 130, 98 and 66, with a mean of 99.3. The 10.7 cm flux was 107.3, 111.7, 112.7, 118.6, 124.9, 121.6 and 119.9, with a mean of 116.7. The estimated planetary A indices were 3, 5, 16, 8, 9, 3 and 3, with a mean of 6.7. The estimated mid-latitude A indices were 3, 3, 10, 7, 6, 3 and 3, with a mean of 5.

On Thursday, I received a Significant Event Report from Rob Steenburgh, KA8JBY, a Space Weather Forecaster at NOAA’s Space Weather Prediction Center: “A trio of significant active regions produced a series of radio blackout (solar flare) events in the past few days. To date, three radio blackouts reaching the R2 (moderate) level have been observed. Earth-directed coronal mass ejections have been associated with each of the biggest radio blackout events on August 2-4. Solar radiation enhancements have also occurred in conjunction with each of these events, with the solar radiation storm event threshold being exceeded to reach the S1 (minor) level in conjunction with the August 4 event.

“Three coronal mass ejections (CMEs) are currently en route to Earth, with the commencement of geomagnetic storming expected early to mid-day on August 5 with the arrival of the CMEs associated with the August 2-3 events. The third of the string, seemingly the fastest CME, may catch up with the first two in the next 12-18 hours, compressing the plasma and enhancing the embedded magnetic field. Storming levels are expected to attain G3 (strong) conditions. The current Solar Radiation Storm may experience a kick with the shocks and attain S2 (moderate) thresholds.

“Some level of geomagnetic disturbance is expected to continue through August 7 as the series of CMEs affect the Earth. Continued activity is likely from these regions as they continue to rotate off the visible solar disk over the next seven days. The Space Weather Prediction Center will continue to monitor this event as it unfolds.”

Thanks, Rob! Check out this NASA video that shows a couple of the CMEs.

The latest forecast on Thursday night has the planetary A index for August 5-9 at 50, 30, 20, 15 and 10, then 8 on August 10-12, then 5, 8, 10, 15, 12, 10 and 8 on August 13-19. The predicted solar flux for August 5 is 115, 110 on August 6-7, 100 and 95 on August 8-9, then 85 on August 10-12 and 100 on August 13-16. The planetary A index at 50 is quite high. Geophysical Institute Prague predicts active conditions on August 5-7, unsettled to active August 8, quiet to unsettled August 9 and quiet conditions August 10-11.

July is over, so let’s look at some of the numbers. The average daily sunspot number for the month of July was 67.2, up from 55.5 for June. The moving three month average of daily sunspot numbers for May through July -- centered on June -- was 61.5. The three month moving average centered on January through June was 35.3, 55.7, 72.3, 74.4, 65.9 and 61.5.

Vince Varnas, W7FA of Portland, Oregon wrote on July 30: “For the last week, the ST0R DXpedition to the Republic of South Sudan has had very weak signal strength here in the Portland area, particularly at night on the 17 meter band (18 MHz). Generally they are S3 at best. At 0209 on July 30, there was a M9 solar flare from a big sunspot. At 0522, I heard and worked the ST0R station on CW with much, much louder signal strength, both directions. (They were at the noise or slightly above a few hours earlier. When I worked them on SSB on July 26 at 2303, they were about S4.) They were S8 to S9. The difference in signal strength between ‘normal’ and last night was about 30 dB. Since it is a scientific fact that solar flares can -- and do -- enhance the reflectivity of the F-layer, my conclusion is that this is what produced the markedly stronger signals from ST0R.”

Thanks, Vince.

Sergej Ignatov, UZ2HZ, of Kremenchug Ukraine, asked about a link to the Penticton source for thrice-daily solar flux readings, as the link he was using no longer works. Yes, they changed servers again, so the URL has changed. Try this in your web browser. The column you want is third from the right, the observed flux values, and the local noon (2000) readings. Although readings are taken three times per day, the noon reading is the official solar flux for the day, also shown here in whole number resolution.

As geomagnetic conditions change over the next few days, you can check here for the planetary K index, updated every three hours. You can also check this every day after 2100 for an updated daily forecast of the solar flux and planetary A index.

Joe Molon, KA1PPV, of Stamford, Connecticut, writes: “Well it happened again. Not much happening southbound, but this time the door to Europe was wide open. I had heard about the M-class flare and decided to check up on solar conditions, as I knew it might get really good before it goes away. I saw a solar flux of 116 with a planetary A index of 3 and a K index of 1, and that is all I needed. In one hour, I logged IZ5RVG, DL2OCE, IC8TEM, IZ5MXA and EB5DZC. This is not that unusual for someone running 100 W into a beam but, as usual, I did it the hard way with 1.5 W, all on 20 meters. I got 599 on all, except for the last when the noise crept up. I was using my Small Wonder Labs PSK kit for 20 meters with 1.5 W into a Diamond BB7V that’s 25 feet above ground level. The propagation gods opened the gate and I walked right through. Wow! It was great to get everyone that I tried for. That never happens in QRPland. Good DX. It's about time!”

Thanks, Joe! Sounds like fun.

All times listed are UTC, unless otherwise noted.

Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears each Thursday in The ARRL Letter. You can find a guide to articles and programs concerning propagation here. Check here and here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.