ARLA/CLUSTER: Previsões de propagação para o mês de Maio pelo Australian Space Forecast Centre

[João Costa > CT1FBF]

Propagation de K7RA


*30 April, 2016*ARLP018

At 0121 UTC on April 29 the Australian Space Forecast Centre released a
geomagnetic disturbance warning for April 30 and May 1.
Increased geomagnetic activity is predicted due to high speed solar wind
coming from a coronal hole. There is a chance of minor storm levels.

Over the past reporting week (April 21-27), average daily sunspot numbers
rose from 40 to 43.3, and average daily solar flux declined from 100.8 to
81.9. This is compared to the previous seven days.

Average planetary A index went from 10.9 to 9.4, and average mid-latitude A
index rose from 8.9 to 11.6.

Predicted solar flux (from the Thursday April 28 forecast) is 95 on April
29-30, 92 on May 1-2, 90 on May 3-4, 95 on May 5-10, 100 on May 11, 95 on
May 12-15, 82 on May 16-24, 80 on May 25, 82 on May 26-29, and 95 on May 30
through June 6.

Predicted planetary A index (also from April 28) is 14, 26, 20, 8 and 5 on
April 29 through May 3, then 12 on May 4-5, 10 on May 6, then 5 on May 7-8,
then 18, 25 and 20 on May 9-11, and 8, 5 and 12 on May 12-14, 5 on May
15-18, then 12, 15 and 12 on May 19-21, 8 on May 22-23, 5 on May 24-25,
then 10, 18 and 12 on May 26-28, and 5 on May 29-30, 12 on May 31, and 5
again on June 1-4.

Petr Kolman, OK1MGW of the Czech Propagation Interest Group sends the
following geomagnetic activity forecast for the period April 29-May 25,
2016.

Geomagnetic field will be:
Quiet on May 6-7, 16-17
Mostly Quiet on May 1-3, 8, 15, 22-25
Quiet to Unsettled on May 12-13, 18, 21
Quiet to Active on April 29, May 4-5, 9-11, 14, 19-20
Active to Disturbed on April 30, May (9-10)

Increases in solar wind from coronal holes are expected on April 29-30, May
4-5, 8-11, 19-21

Remarks: Parenthesis means lower probability of activity enhancement.

NASA released a video of an April 17 solar flare:
http://bit.ly/1WU1nOO

Ted Leaf, K6HI of Kona sent this similar item:
http://earthsky.org/space/stunning-view-of-solar-flare-april17-2016?

Spaceweather.com reports Earth will cross a fold in the heliospheric
current sheet on April 29 or 30.
http://wso.stanford.edu/gifs/HCS.html

They go on to report, "This is called a 'solar sector boundary crossing,'
and it could trigger geomagnetic activity around Earth's poles. NOAA
forecasters estimate a 60 percent chance of G1-class geomagnetic storms on
April 29."

We see there were multiple sunspots in evidence in this view of April 28,
although none have much magnetic strength:
http://bit.ly/21gMPsW

Now on April 29, you can see the sunspots have moved in one day:
http://bit.ly/1SCKUt1

Sharp-eyed reader Red Willoughby, KC4LE of Birmingham, Alabama noticed some
averages that didn't look right in the ARRL Letter released yesterday,
April 28. He may have wondered why the average daily solar flux was over
100, when all of the daily flux values for the week were under 100.

I goofed. The numbers were all correct, but the averages were from last
week. Those averages have been corrected in today's bulletin.

If you would like to make a comment or have a tip for our readers, email
the author at, k7ra  arrl.net

For more information concerning radio propagation, see the ARRL Technical
Information Service at
http://arrl.org/propagation-of-rf-signals.

For an explanation of the 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/

My own archives of the NOAA/USAF daily 45 day forecast for solar flux and
planetary A index are in downloadable spreadsheet format at
http://bit.ly/1VOqf9B and http://bit.ly/1DcpaC5 .

Click on "Download this file" to download the archive and ignore the
security warning about file format. Pop-up blockers may suppress
download.

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 21 through 27 were 35, 22, 11, 46, 38, 65, and
86, with a mean of 43.3. 10.7 cm flux was 76.8, 76.6, 78.7, 81.8, 81.9,
85.2, and 92.6, with a mean of 81.9. Estimated planetary A indices were 5,
13, 12, 11, 8, 7, and 10, with a mean of 9.4. Estimated mid-latitude A
indices were 23, 13, 11, 11, 6, 6, and 11, with a mean of 11.6.
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