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The K7RA Solar Update



"Four halo CMEs first observed over 08-09 May are expected to arrive
at Earth on 10-May, starting at 1000 UTC +/- 10 hours. G4
geomagnetic conditions are expected on 10-May, reducing to G3 with a
chance of G4 on 11-May.



"10 May: G4
11 May: G3, chance of G4
12 May: G1"

Six new sunspot groups appeared this reporting week, May 2-8, one
each day on May 2-4, two on May 5 and another on May 6. On May 9 two
more sunspot groups emerged, and the daily sunspot number rose to

Average daily sunspot number increased from 124.6 to 138.3, and
average daily solar flux rose from 144.9 to 177.6.

Average daily planetary A index climbed from 9.6 to 14.4, while
middle latitude numbers went from 8.6 to 12.3.

The most active day was May 2, when the planetary A index was 44.
Alaska's College A index was 61. The cause was two CMEs striking
Earth, causing a G3 class geomagnetic storm.

The solar flux is peaking now and may peak again around June 11-12
at 205.

Predicted solar flux is 240 and 225 on May 10-11, 220 on May 12-13,
then 215 on May 14, then 210 on May 15-16, and 200, 195, 190, 185,
180, 175, 170, 165 and 170 on May 17-25, then 175 on May 26-27, 170
on May 28, then 165 on May 29-31, then 175, 180, 185, 190 and 185 on
June 1-5, 175 on June 6-9, 180 on June 10, 205 on June 11-12, then
200, 195, 190 and 185 on June 13-16.

Predicted planetary A index is 8, 5, 8, 12 and 10 on May 10-14, 5 on
May 15-22, then 8, 12, 8, 5, 12 and 8 on May 23-28, then 5, 5 and 8
on May 29-31, and 12 on June 1-3, then 8, 10, 5 and 5 on June 4-7,
then 8, 15 and 10 on June 8-10, and 5 on June 11-18.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - May 9, 2024 from OK1HH.

"This week, the number of sunspot groups was smaller than in
previous weeks (decreased from nine on Monday to six on Wednesday),
but two of them (AR3663 and AR3664) are really big. Moreover, both
have a beta-gamma-delta magnetic configuration, indicating the
possibility of producing strong solar flares. Moderate flares
(M-class) were observed several times a day and large flares
(X-class) were not an exception.

"Although AR3663 is now approaching the northwestern limb of the
solar disk, the overall solar activity is certainly not decreasing,
quite the contrary: AR3664 continued to grow rapidly, and has merged
with neighboring AR3668 to rival the large Carrington spot of 1859
in size. If it were to produce a CME eruption similar to 1859, and
if the CME were to hit the Earth, the so-called 'Carrington Event'
could be repeated, with potentially devastating consequences for
power and communications grids.

"So far, on the lower shortwave bands, we have seen rapid and large
increases in attenuation during large flares, up to and including
disruption of communications for tens of minutes to hours. The
phenomenon is abbreviated SWF (Shortwave Fading), belongs to the SID
(Sudden Ionospheric Disturbance) group. SWF is named after two
physicists, John Howard Dellinger and Hans Mogel, as the Dellinger
effect, or sometimes Mogel-Dellinger effect.

"Solar flares with CMEs in the western half of the solar disk appear
to be followed by an increase in geomagnetic activity and a marked
fluctuation in shortwave propagation conditions around the weekend,
with a slow return to average conditions in the following days."

Recent reports from Dr. Tamitha Skov, WX6SWW:

Today's large sunspot comparable to Carrington Event:

Not like Carrington event:

Northern lights:

Really big sunspots:

Flare attacks Earth:

May 11 warning on X-Class Solar Flares:

Celestial onslaught of three Solar Flares:

Solar storm train:

Aurora in Oregon and Washington.

More on Solar Storms:

Send your tips, reports, observations, questions, and comments to When reporting observations, don't forget to tell us
which mode you were operating.

For more information concerning shortwave radio propagation, see and the ARRL Technical Information
Service web page 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 .

Also, check this QST article about Solar Indices:

Instructions for starting or ending email distribution of ARRL
bulletins are at .

Sunspot numbers for May 2 through 8 2024 were 125, 121, 136, 152,
148, 144, and 142 with a mean of 138.3. 10.7 cm flux was 141.9, 156,
166.6, 176.9, 171.2, 203.6, and 227.1, with a mean of 177.6.
Estimated planetary A indices were 44, 10, 6, 12, 15, 7, and 7, with
a mean of 14.4. Middle latitude A index was 24, 16, 5, 12, 13, 6,
and 10, with a mean of 12.3.




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