We haven’t seen a sunspot since Thursday, April 30 when the daily sunspot number was 35. This is a relatively high sunspot number based on recent activity, although not historically. In fact, the daily sunspot number has not been as high since March 21, 2019 when it was 49, and prior to that we need to look back further to the previous year, when the daily sunspot number was 41 on June 22, 2018, to find a sunspot number that was as high.
This, and the fact that last week’s sunspots showed the new Cycle 25 polarity gives me reason for optimism. I expect solar activity to increase and along with it, the outlook for better HF propagation. Another reason for my optimism is that new sunspot cycles increase at a faster rate than they decline after an activity peak has passed.
That peak of sunspot Cycle 25 is expected around July 2025, +/- 8 months, according to the latest forecast from the NOAA/NASA International Solar Cycle Prediction Panel.
Average daily sunspot number for last week was 5, down from 8.7 the previous seven days. The average daily solar flux rose from 69.2 to 69.5.
Average daily planetary A index declined from 5.6 to 5.1, and average middle latitude A index slipped from 5.1 to 5.
Predicted solar flux over the next 45 days is 70, every day, May 8 until June 21. In fact, that outlook for a continuous 45-day stretch of solar flux at 70 has been the same since the May 3 prediction.
The predicted planetary A index is 5 on May 8-11, 8 on May 12, 5 on May 13-17, then 10 and 8 on May 18-19, 5 on May 20-23, 8 on May 24-27, 5 on May 28-30, then 8, 10 and 8 on May 31 through June 2, 5 on June 3-13, 10 and 8 on June 14-15, and 5 on June 16-21.
There you have it, a nice steady solar flux above the sixties for the next month and a half, and stable geomagnetic conditions too.
On Thursday, May 7, Spaceweather.com reported an incoming solar wind expected to graze our magnetic field on May 10, “causing geomagnetic unrest at high latitudes.” Note that our planetary A index forecast above does not show an increase until May 12.
Geomagnetic activity forecast for the period May 8 until June 2, 2020 from F.K. Janda, OK1HH.
Geomagnetic field will be
quiet on: May 13, 26, June 2
quiet to unsettled on: May 8, 16, 25, 27-31
quiet to active on: (May 9, 11-12, 14-15, 20-22, 24, June 1)
unsettled to active on: (May 10, 17-19, 23)
active to disturbed: nothing expected
Solar wind will intensify on: May (11-12,) (18-21, 23,) 24
– Parenthesis means lower probability of activity enhancement.
– The predictability of changes remains lower as there are no indications.
Jon Jones, N0JK, reported on May 6: “I was active on 50 MHz during the Eta Aquarid meteor shower on May 5. I worked W4IMD EM84 on 6 meters via meteor scatter using the digital MSK144 mode at 1205 UTC. As W4IMD sent 73, I copied a CQ from Larry Lambert, N0LL, who was portable in rare grid DN90. I called Larry, he copied me, but we did not complete a contact.
“I decoded several other stations including N4QWZ, AI5I, K0TPP, KE5Q, and WA4CQG on meteor scatter.”
Check https://bit.ly/3fwUP6P for a dramatic video from Space.com showing images of all daily earth-facing sunspot activity over seven years, including approximately 93 solar rotations, compressed into 200 seconds.
Frank Donovan, W3LPL, sent this fascinating information on Earth’s three north poles. “BBC’s article this week ‘Scientists Explain Magnetic Pole’s Wanderings’ has attracted the interest of radio amateurs interested in ionospheric propagation.
“Unless you’ve studied geomagnetic physics, you probably never learned — or even heard — that the Earth has three north poles. The BBC article describes the poles very well but does not address the relationship between the poles and ionospheric propagation.
“The geographic north pole is where the Earth’s rotation axis intersects the Earth’s surface in the northern hemisphere. It affects ionospheric propagation because the orientation of Earth’s tilted axis to the Sun varies with the seasons and determines our daylight/darkness cycles throughout the year.
“While the magnetic north pole — the focus of the BBC article — is important to navigation systems, it has no significance to ionospheric propagation. Most of us learned about the magnetic north pole when we learned how to use a compass, it is in the northern hemisphere where the Earth’s magnetic field lines are measured to be exactly perpendicular to the Earth’s surface. Its position has been drifting about 50-60 km per year for about the last forty years.
“The geomagnetic north pole — only briefly described in the BBC article — is particularly important to ionospheric propagation and many other aspects of the Earth’s space environment. It is the intersection of the Earth’s surface in the northern hemisphere and the axis of a bar magnet hypothetically placed at the center the Earth. It is significant for ionospheric propagation because it determines the position of the geomagnetic field in the Earth’s space environment including — very importantly –its ionosphere. The geomagnetic field very profoundly affects ionospheric propagation. The geomagnetic north pole drifts only about one km. per year, a tiny fraction of the movement of the magnetic north pole described in the BBC article. See https://ichef.bbci.co.uk/news/624/cpsprodpb/13DC2/production/_112164318_new-nc.png.
“As an aside, while the magnetic north pole is drifting fairly rapidly, the magnetic south pole is drifting very little at all.”
If you would like to make a comment or have a tip for our readers, email the author at email@example.com.
For more information concerning radio propagation, see http://www.arrl.org/propagation and the ARRL Technical Information Service at http://arrl.org/propagation-of-rf-signals. For an explanation of 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/.
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 April 30 through May 6, 2020 were 35, 0, 0, 0, 0, 0, and 0, with a mean of 5. 10.7 cm flux was 69.8, 70.2, 69.2, 68.7, 69.3, 69.3, and 69.8, with a mean of 69.5. Estimated planetary A indices were 2, 6, 5, 5, 6, 6, and 6, with a mean of 5.1. Middle latitude A index was 1, 5, 3, 5, 8, 7, and 6, with a me
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