Again this week solar indices crept lower. Average daily sunspot numbers declined 8 points to 20.4, and average daily solar flux went down 2.4 points to 86.4. Geomagnetic indices softened, with planetary A index down 3 points to 8.9, and mid-latitude A index down 1.2 points to 7.4.

Just one new sunspot appeared since March 17, and that was one week later on March 24.

Predicted solar flux values from USAF and NOAA saw a major downward shift on March 28. Overnight, the predicted average daily solar flux for the 38 days from April 4 through May 11 dropped from 91.6 to 82.2. You can see this by downloading the spreadsheet at http://bit.ly/1VOqf9B .

Predicted solar flux is 82 on April 1, 81 on April 2-3, 80 on April 4-5, 75 on April 6, 80 on April 7-9, 85 on April 10-11, 80 on April 12-17, 85 on April 18-24, 80 on April 25-28, 85 on April 29 through May 2, and 80 on May 3-6.

If the daily solar flux declines to 75 as predicted for April 6, it will be the lowest flux value since the other side of this solar cycle, when it was 74.8 on November 22, 2010.

Predicted planetary A index is 10, 26 and 18 on April 1-3, then 8, 18, and 14 on April 4-6, 10 on April 7-8, 5 and 10 on April 4-8, then 5, 15, 24, 22 and 20 on April 9-13, then 8 on April 14-15, and 5 on April 16-22, 12 on April 23-24, 8 on April 25, then 5 on April 26-28, then 25 on April 29-30, 8 on May 1, and 5 on May 2-4. The A index then rises to 24, 22 and 20 on May 8-10.

From Petr Kolman, OK1MGW of the Czech Propagation Interest Group:

Geomagnetic activity forecast for the period April 1-27, 2016.

Geomagnetic field will be:
Quiet on April 20-22
Mostly quiet on April 1, 14, 17-19, 27
Quiet to unsettled on April 5-6, 9, 10, 15-16, 25-26
Quiet to active on April 4, 7-8, 13, 23-24
Active to disturbed on April 2-3, 11-12

Increased solar wind from coronal holes are expected on April 1-4, 7-8, 10-13, and 23-24

Do you like the new format for the above report? Whether you do, or not, or don’t care, register your opinion at https://www.surveymonkey.com/r/BP9FMTZ

According to Spaceweather.com, “NOAA forecasters estimate a 45 percent chance of polar geomagnetic storms on April 1 when a CIR is expected to hit Earth's magnetic field. CIRs (co-rotating interaction regions) are transition zones between fast and slow-moving solar wind streams. Density gradients and shock waves inside CIRs often do a good job sparking auroras.”


Here is a fascinating phenomenon reported by Jon Jones, N0JK: “I was on 10 meters fixed mobile this afternoon (March 27) playing in the CQ WPX SSB on 10 meters. At around 2050Z I was calling CU2ARA. When I released the mic button, I heard ‘Japan Kilowatt.’ I called again, released the push-to-talk switch, and heard the same response. It sounded like my voice, but shifted down 500 Hz or so, with a 5 X 5 strength and a hollow auroral-type sound.

“I called several times to test it, saying my call once and releasing the switch, and I heard it every time! I went down the band and called CN2AA after working the CU2. I heard the same echo for a couple of calls, and then it was gone by 2100z.

“It takes about 2 seconds to speak the phonetics ‘Japan Kilowatt.’ Considering how far my signal would have traveled in that amount of time, I don’t understand how there could be enough energy left for me to receive, much less at a 5 X 5 level.

“I suppose someone may have recorded my call and was playing it as deliberate QRM, but their timing would have to be awfully precise to play it every time I called, and on different spots on the band and only when the DX was listening, not transmitting.

“The distance for single-hop F2 backscatter would be too short. I recall the K5CM tests for backscatter echoes on 6 and 10 meters. They are a fraction of a second. Ten meters was very loud to the Caribbean and West Africa at the time, as well as New Zealand.”

On a different subject, N0JK also commented: “I logged the VK0EK DXpedition March 28 on 30 meter CW. They had just come up on 30 meters at 0250z and worked them ‘down 1 kHz.’ My set up is 100 watts and my antenna is the rain gutter on our home! Catching VK0EK in the clear and before the pileup found them was a treat! 30 meters is an amazing band.”


A widely-held misconception is that space weather stalls and becomes uninteresting during periods of low sunspot number. In fact, by turning the solar cycle sideways (see https://www.vsp.ucar.edu/Heliophysics/pdf/Lika_sideways_SC.pdf ), we see that Solar Minimum brings many interesting changes. For instance, the upper atmosphere of Earth collapses, allowing space junk to accumulate around our planet. The heliosphere shrinks, bringing interstellar space closer to Earth. Also, galactic cosmic rays penetrate the inner solar system with relative ease.

Let’s take a look at our 3-month moving average of sunspot numbers. The average for the three month period centered on February 2016 (including all daily sunspot numbers from January 1 through March 31) was 49. This is the lowest number seen since January 2011, when it was 35.3. The moving average peaked in March, 2014 when it was 148.2. Since May 2015 the averages were 77.7, 76.3, 69.1, 67.5, 64.5, 64.6, 58.5, 55.4, 53.5 and 49.


A nice image of lone sunspot 2526 is at https://www.astrobin.com/243353/G/ . It was photographed by astrophotographer Alexander Sorokin in his backyard at Azov, in Rostov oblast in the Russian Federation.

David Moore sent this link to yet another article about superflares. This one speculates about bigger flares on distant stars, and wonders if they could happen here in our solar system. I wouldn’t pay much attention to the speculation in comments at the end of this piece, about our Earth being overdue for such an event. Seems to me that claiming we are due for another one is the same logic as the Gambler’s Fallacy (see https://en.wikipedia.org/wiki/Gambler's_fallacy ).

Here is the article: http://earthsky.org/space/could-our-sun-emit-killer-superflare


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 at http://arrl.org/w1aw-bulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us/.

My own archives of the NOAA/USAF daily 45 day forecast for solar flux and planetary A index are in downloadable spreadsheet format at http://bit.ly/1VOqf9B and http://bit.ly/1DcpaC5 .

Click on “Download this file” to download the archive, and ignore the security warning about file format. Pop-up blockers may suppress the download.

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 at http://arrl.org/bulletins.

Sunspot numbers for March 24 through 30 were 25, 24, 23, 23, 23, 13, and 12, with a mean of 28.4. 10.7 cm flux was 86.5, 85.5, 85.5, 88.2, 87.7, 87.8, and 83.8, with a mean of 88.8. Estimated planetary A indices were 7, 6, 3, 13, 10, 11, and 12, with a mean of 11.9. Estimated mid-latitude A indices were 7, 6, 2, 10, 9, 8, and 10, with a mean of 8.6.