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At 2256 UTC on June 16 the Australian Space Weather Forecast Centre
issued a geomagnetic warning, The solar wind speed on UT day 15 Jun
has increased as the Earth entered a coronal hole wind stream after
15/0545UT. Increased geomagnetic activity is expected for 16 Jun
with isolated periods of G1 Minor level activity.  Earlier in the
day I checked the NOAA planetary K index page, and it showed a jump
from K index of about 1.8 at 1200 UTC to about 4.1 at 1500 and again
at 1800 UTC, then about 4.5 at 2100 UTC and 5.5 at 0000 UTC on June
16. At 0300 UTC it was down a bit to 5.  Solar activity declined
this week, with average daily sunspot numbers dropping from 139 to
122, while average daily solar flux decreased from 166.8 to 154.8.
This compares the current reporting week of June 8 to 14 against the
previous seven days.  Average daily planetary A index decreased from
7.3 to 5.7, and average daily middle latitude A index from 8.6 to
6.7.  On June 14 Spaceweather.com reported two new sunspot groups
emerging across the Suns southeastern horizon.  Forecasters Cundiff
and Trost of the U.S. Air Force 557th Weather Wing predict solar
flux at 155 on June 16 and 17, 160 on June 18 and 19, then 155, 160
and 165 on June 20 to 22, 170 on June 23 to 25, then 168, 165 and
162 on June 26 to 28, 160 on June 29 through July 4, 165 on July 5,
170 on July 6 to 8, then 155, 157, 153 and 160 on July 9 to 12, 150
on July 13 and 14, 155 on July 15 to 17, then 160 and 165 on July 18
and 19, and 170 on July 20 to 22.  Predicted planetary A index is
18, 12 and 8 on June 16 to 18, 5 on June 19 and 20, 8 on June 21 and
22, 5 on June 23 to 26, 12 on June 27 and 28, 5 on June 29 and 30,
then 12 and 8 on July 1 and 2, 5 on July 3 to 7, 12 on July 8 to 10,
then 5, 5, and 12 on July 11 to 13, and 10 on July 14 and 15, and 5
on July 16 to 23.  These predictions look great for ARRL Field Day,
which is June 24 and 25. Why? Solar flux peaks at 170 on June 23 to
25, and the predicted planetary A index is a nice quiet 5 on June 22
to 26. Next week we will present an updated forecast just prior to
Field Day weekend.  Weekly Commentary on the Sun, the Magnetosphere,
and the Earths Ionosphere June 16, June 22, 2023 from F.K. Janda,
OK1HH.  The first half of June was quieter than May, both on the Sun
and in the Earths magnetosphere and ionosphere.  However,
helioseismic maps of the far side of the Sun showed a number of
large active regions, probably sunspots. We therefore expected an
increase in activity. But thats not likely to happen until a week
from now.  Even so, there were some rather unexpected eruptions of
moderate magnitude during the local midday, which triggered a SWF,
Shortwave Fading, that could have broken the QSO in the longer half
of the shortwave band.  Meanwhile, we observed a coronal hole in the
solar equator region that crossed the central meridian on June 12.
Associated with it is the co rotating interaction region, CIR, which
are the transition zones between the slow and fast solar wind
streams. Since the accumulation of solar plasma in the solar wind
results in structures that are similar to the arrival of a CME, we
expected a geomagnetic storm on the evening of 15 June UTC. The
estimate was quite accurate, the disturbance began at 1500 UTC.  We
can expect the geomagnetic field to be active for a few more days,
including smaller storms.  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.  The multiple websites mentioned in this bulletin
can be found in teleprinter, packet, and Internet versions of 2023
Propagation Forecast Bulletin ARLP024.  Sunspot numbers were 149,
152, 116, 116, 116, 98, and 107, with a mean of 122. 10.7 cm flux
was 168.5, 164.3, 161.2, 153.8, 146.1, 146.3, and 143.5, with a mean
of 154.8.  Estimated planetary A indices were 5, 4, 5, 9, 6, 6, and
5, with a mean of 5.7. Middle latitude A index was 6, 6, 4, 10, 8,
8, and 5, with a mean of 6.7.

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