= NOW 18 WPM transition file follows =

This reporting week, May 11 to 17, average daily sunspot number was
nearly the same as last week, 118.6 compared to 119.3, only
marginally lower.  But average daily solar flux dropped from 167.8
to 143.2.  Geomagnetic indicators were quieter, both planetary and
middle latitude A index at 9.6. Last week the two numbers were 15.1
and 11.9, respectively.  What is the outlook for the next few weeks?
10.7 cm solar flux is forecast to have a peak of 165 on June 8.  The
predicted numbers are 145 on May 19, 140 on May 20 and 21, 135 on
May 22 to 24, 140 on May 25 and 26, 145 on May 27, 155 on May 28 to
30, 160 on May 31 and June 1, 155 on June 2 and 3, 160 on June 4 to
7, then 165, 160, 150, 145, and 150 on June 8 to 12, then 155 on
June 13 to 17, 150 on June 18, 145 on June 19 to 21, 140 and 145 on
June 22 and 23, and 155 on June 24 to 26 then 160 on June 27 and 28.
Predicted planetary A index is 5, 8, 12, 15 and 5 on May 19 to 23,
12 on May 24 and 25, 15 on May 26, 10 on May 27 and 28, 8 on May 29,
5 on May 30 through June 1, then 16, 12, 16 and 12 on June 2 to 5, 8
on June 6 to 8, then 5 on June 9 to 18, 12 and 20 on June 19 and 20,
15 on June 21 and 22, 10 on June 23 and 24, 8 on June 25, and 5 on
June 26 to 28.  These numbers are updated daily here,
//services.swpc.noaa.gov/ .  Thanks to reader David Moore for this,
And article about how 1,000 undergraduates helped solve an enduring
mystery about the Sun can be found at,
//www.sciencedaily.com/releases/2023/05/230509122026.htm .  For
three years at the height of the COVID 19 pandemic, a group of
students spent an estimated 56,000 hours analyzing the behavior of
hundreds of solar flares. Their results could help astrophysicists
understand how the Suns corona reaches temperatures of millions of
degrees Fahrenheit.  Weekly Commentary on the Sun, the
Magnetosphere, and the Earths Ionosphere, May 18, 2023, from F.K.
Janda, OK1HH.  On May 12, we expected a CME impact from the flare on
the evening of May 9. It was indeed registered, at 0635 UTC the
geomagnetic storm began. However, it was weaker than expected, of G1
class.  On 13 May at 1915 UTC, an unexpected CME impact followed for
a change, which again triggered another G1 class geomagnetic storm.
On 16 May, we expected another smaller CME. The particle cloud has
been slowly approaching Earth since the magnetic filament eruption
in the southern hemisphere of the Sun on 12 May.  The next solar
flare on May 16, with a maximum at 1643 UTC, was M9.6 class. It came
from a sunspot group still hiding behind the southeastern limb of
the Sun. In fact, it may have been an X flare, partially obscured by
the solar horizon. Yet it caused the strong Dellinger effect,
shortwave fade, over North America.  After the sunspot group came
out on the solar disk, we could observe it as AR 3310. Its about
three times wider than Earth, and its magnetic configuration
promises more flares.  Not only was solar flare activity quite high,
but the Sun was hurling so many CMEs into space that hardly a day
went by without one hitting Earth. Therefore, the frequency of
geomagnetic storms was also higher, followed by frequent
deterioration of shortwave propagation conditions. In summary, the
25th solar cycle continues to evolve nicely.  A video from Dr.
Tamitha Skov, WX6SWW, is available on youtu.be .  The links to
various online stories about the Sun, massive solar flares, and
radio blackout are available in digital versions of this bulletin.
If you would like to make a comment or have a tip for our readers,
please email the author at, k7ra at arrl.net.  When reporting
observations, dont forget to tell us which mode you were operating.
For more information concerning radio propagation, see the ARRL
Technical Information Service web page.  A detailed explanation of
the numbers used in this bulletin is also available on this site.
An archive of past propagation bulletins is also available.  Sunspot
numbers were 152, 134, 120, 109, 103, 106, and 106, with a mean of
118.6. 10.7 cm flux was 163.4, 149.1, 143.8, 139.7, 134.5, 134.3,
and 137.9, with a mean of 143.2.  Estimated planetary A indices were
9, 19, 13, 8, 6, 8, and 4, with a mean of 9.6. Middle latitude A
index was 10, 15, 12, 9, 6, 10, and 5, with a mean of 9.6.

= END OF 18 WPM transition file <