The K7RA Solar Update


Since we are now at (or close to) the peak of Solar Cycle 24, it is no surprise that the solar indices are up. The latest forecast predicts Solar Cycle 24 to peak this fall, but that will be determined after the fact, and it will be based on a long running average of sunspot numbers. This past week, the average daily sunspot numbers increased by more than 34 points, rising to 156.1, while the average daily solar flux was up by nearly 3 points to 140.1. On May 15, the daily sunspot number was 186 -- the highest number since January 6-7, when the sunspot number was 186 and 196, respectively.

Sunspot numbers for May 9-15 were 154, 149, 145, 173, 144, 142 and 186, with a mean of 156.1. The 10.7 centimeter flux was 128.4, 124.8, 136.6, 147.3, 150.3, 147.9 and 145.6, with a mean of 140.1. The estimated planetary A indices were 5, 5, 4, 5, 6, 8 and 9, with a mean of 6. The estimated mid-latitude A indices were 4, 4, 4, 6, 6, 7 and 10, with a mean of 5.9.

The predicted solar flux for the near term is 145 on May 17-18, 140 on May 19, 135 on May 20, 130 on May 21, 125 on May 22, 120 on May 23-24, 160 on May 25, 170 on May 26, 160 on May 27-28, 155 on May 29-30, 150 on May 31, 155 on June 1, 160 on June 2-3, 155 on June 4, 150 on June 5, and back down to 145 on June 6-8. The predicted planetary A index is 15 on May 17, 8 on May 18-19, 5 on May 20, 8 on May 21, 15 on May 22, 12 on May 23, 8 on May 24, 5 on May 25-27, 15 and 10 on May 28-29, 5 on May 30-June 8, 8 on June 9, and 5 on June 10 and rising to 12 on June 11.

Today (May 17), is reporting that a coronal mass ejection (CME) may strike Earth today, but it is expected to be a glancing blow instead of a direct hit. The CME is from an X1-class flare that exploded two days ago from sunspot group 1478; this group should be pointing directly at Earth within a few days. NOAA is predicting a 40 percent chance of polar geomagnetic storms. Both ZDNet and have stories about these solar flares.

David Moore sent a link to a video from Phil Plait’s “Bad Astronomy” blog on This entry, “The Beauty of Reality,” features what Plait calls “a superb and compelling time-lapse animation of the night skies over Michigan.” The video, North Country Dreamland by photographer Shawn Malone, runs almost seven minutes. It’s a pretty high bandwidth HD video, so if you have an average broadband connection, you may want to turn off the audio and walk away from the computer for a while and let the buffer load up on data, then run the video from the beginning.

There are a couple of space weather pages on Facebook that might be of interest to hams. You will have to sign up for Facebook to read these, but it is free and painless. Check out the NOAA NWS Space Weather Prediction Center page and the Space Weather and Radio Resources at page. You also might want to check out the HF Radio & Space Weather Panel website, run by Ismael Pellejero Ibáñez, EA4FSI. Scroll down the page for “Solar Flux Index and Sunspots” for an interesting plot correlating proton flux, solar flux and sunspot numbers.

Jon Jones, N0JK, of Lawrence, Kansas, wrote: “Every dog has his day. I worked Luis, LU9EHF (grid square FF95), in Argentina on 50.130 MHz with 5 × 9 signals at 2159 UTC on May 10. I was running 100 W to a dipole antenna in the attic over the garage. At 2145 UTC, K0HA (grid square EN10) in Nebraska spotted Luis on 50.130 MHz. I tuned in not expecting to hear anything, but I heard some weak Spanish-accented SSB on frequency. It was LU9EHF. He worked a W8, and then suddenly got much louder -- very loud, way over S-9. He worked N0LWF (grid square EN10wm) in Nebraska at 2157 UTC. I waited anxiously for them to finish their contact. LU9EHF called QRZ and I dropped my call in. Bam! Luis came right back and we exchanged reports. Luis is in grid square FF95, a little more than 8900 kilometers away.

“I recorded parts of LU9EHF’s QSOs with K9KU (grid square EN61) in Wisconsin and WF0N (EM28) in Kansas after I signed with him. Luis was so loud that the speaker on the radio was distorting. I suspect a fairly high wave angle to the E-skip link, given the strength of LU9EHF’s signal on the dipole. Perhaps a chordal hop E-skip linking to to trans-equatorial propagation? It was one of the more remarkable things I have heard on 6 meters.”

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.