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The K7RA Solar Update


We only saw sunspots over two days of this past week, March 30 and 31 when the daily sunspot numbers were 11 and 12. There were no sunspots during the previous week, so the average daily sunspot number rose from 0 to 3.3.

Average daily solar flux changed from 68.2 to 68.6.

Geomagnetic indicators were quiet, with average daily planetary A index declining from 10.6 to 5, and average mid-latitude A index going from 8.9 to 4.

The averages for solar flux and A index shown at the end of last week’s bulletin were incorrect, and have been corrected above. Thanks to AA2F for discovering my error.

Predicted solar flux is 67 on April 6-12, 68 on April 13-22, 69 on April 23 through May 6, 68 from May 7-19 and 69 on May 7.

Predicted planetary A index is 8 on April 6, 5 on April 7-9, then on April 10, 15 on April 11-12, 18 on April 13-14, then 15, 10, 5 and 8 on April 15-18, 15 on April 19-21, then 12 and 10 on April 22-23, then 5 on April 24 to May 6, then 10, 15 and 20 on May 7-9. 18 on May 10-11, then 15, 10, 5 and 10 on May 12-15, then 15 on May 16-18 and 12 and 10 on May 19-20.


F.K. Janda, OK1HH sent this geomagnetic activity forecast for the period April 6 to May 1, 2018.

Geomagnetic field will be:

Quiet on April 8-9, 24-25, 27-29, May 1

Mostly quiet on April 19, 26, 30

Quiet to unsettled on April 7, 10, 16-18, 23

Quiet to active on April 6, 11, 13, 15, 20-22

Active to disturbed on April 12, 14

Solar wind will intensify on April (6-8,) 10-18, 23-25, (27-30)


- Parenthesis means lower probability of activity enhancement.



Mark Bell, K3MSB, of Airville, Pennsylvania reported on April 5: "I’ve been trying to work Australia for quite a while on 160 meters. During the current 160-meter season, I’ve heard bits and pieces of calls from Australia, and occasionally a complete call, but nothing strong enough to work.

“Saturday morning, March 31, I was on 160 meters around 1030Z. I saw Ron, VK3IO, spotted and tuned to his frequency and was astounded at his signal strength! He was a nice 559, almost armchair copy as the saying goes. I was even more stunned that he answered my first call and received a 579 from him at 1045Z, which is about 35 minutes before my sunrise.  At 1101Z I had the pleasure of working Luke VK3HJ, who was not as strong as Ron, but putting in a very nice signal. My receive antenna is a 200-foot RBOG (Reversible Beverage on Ground) oriented NW/SE and my transmit antenna is an inverted-L.

“On Wednesday, April 4, 160 meters was pretty dead around 1030Z so I started calling CQ. A few kHz above me, Jon, AA1K, was also calling CQ. Phil, VK6GX, spotted Jon at 1024Z and me at 1033Z. Later I e-mailed Phil and he said while he heard us, we were both too weak to make contact.

“Phil also stated that openings from VK6 to the East Coast have been few and far between in the last few years. Signals often don't make it across the Nullarbor Plain to VK6."


Interesting article on the history of solar photography:


From Tamitha Skov: "Outside of the bright region this week being a lot quieter and weaker than we hoped, we have a remnant coronal hole sending small pockets of fast solar wind our way. This is good news for aurora photographers at high latitudes, but it also brings a little more zing to the ionosphere for amateur radio operators and emergency responders suffering with low solar flux right now. 

“Radio propagation on Earth's day side will likely remain poor, but you might be surprised how a slight bit of activity can really perk up the radio bands at night and in the gray line. GPS users should also enjoy better than average GPS conditions on Earth's night side, even at low latitudes where night time is often troublesome for GPS.

“But don't expect these conditions to last for more than a few days. Next week we will be dealing with a more serious chance of reaching solar storm conditions, when a much bigger coronal hole rotates into the Earth-strike zone."



For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of numbers used in this bulletin, see

An archive of past propagation bulletins is at More good information and tutorials on propagation are at

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 March 29 through April 4, 2018 were 0, 11, 12, 0, 0, 0, and 0, with a mean of 3.3. 10.7 cm flux was 69, 68.8, 69, 69, 68.4, 67.8, and 68.5, with a mean of 68.6. Estimated planetary A indices were 4, 5, 7, 5, 5, 4, and 5, with a mean of 5. Estimated mid-latitude A indices were 3, 4, 6, 4, 4, 3, and 4, with a mean of 4.





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