[SFDXA] ARLP035 Propagation de K7RA

Fri Aug 27 20:26:26 EDT 2021

> SB PROP @ ARL $ARLP035
> ARLP035 Propagation de K7RA
> 
> ZCZC AP35
> QST de W1AW  
> Propagation Forecast Bulletin 35  ARLP035
> From Tad Cook, K7RA
> Seattle, WA  August 27, 2021
> To all radio amateurs 
> 
> SB PROP ARL ARLP035
> ARLP035 Propagation de K7RA
> 
> Sun watchers saw no days without sunspots this week.  Average daily
> sunspot numbers rose from 17.7 last week to 21.7 this reporting
> week, August 19 through 25.
> 
> Average daily solar flux increased from 73.8 to 78.5.
> 
> Geomagnetic indicators were quiet, with average daily planetary A
> index declining from 6.1 to 4.7, and average daily middle latitude A
> index dropping from 7.6 to 5.7.
> 
> We are less than one month away from the Northern Hemisphere
> autumnal equinox, on Wednesday, September 22, 2021.  Both
> hemispheres will be bathed in equal measures of solar radiation,
> always a positive for HF propagation.
> 
> Predicted solar flux is 90 on August 27 to September 2, 85 on
> September 3, 73 on September 4 to 11, 74 on September 12 to 15, 76
> on September 16 to 18, 77 on September 19 and 20, 76 on September
> 21, 75 on September 22 to 29 and 73 on September 30 through October
> 8.
> 
> Predicted planetary A index is 16, 12, 10 and 8 on August 27 to 30,
> 5 on August 31 through September 1, 8 and 12 on September 2 and 3, 5
> on September 4 to 10, then 10 and 8 on September 11 and 12, 5 on
> September 13 to 18, 8 on September 19 and 20, 15 and 10 on September
> 21 and 22, 7 on September 23 and 24, 5 on September 25 to 28, then 8
> and 12 on September 29 and 30 and 5 through the first week in
> October.
> 
> I find it encouraging that the above solar flux forecast from USAF
> and NOAA was revised upward over the past few days, and that the
> sunspot number (47) on Thursday, August 26 was much higher than the
> average daily sunspot number (21.7) over the previous seven days.
> 
> Geomagnetic activity forecast for the period August 27 til September
> 21, 2021 from F. K. Janda, OK1HH.
> 
> "Geomagnetic field will be 
> Quiet on September 1, 5, 10, 14 to 18
> Quiet to unsettled August 28, 31, September 2 to 4, 6 to 9, 19 and 20 
> Quiet to active on August 29 and 30, September 11 to 13, 21
> Unsettled to active August (27)
> Active to disturbed, Nothing predicted
> 
> Remarks:
> - Parenthesis means lower probability of activity enhancement."
> 
> At 0839 UTC on August 26 the Australian Space Forecast Centre issued
> a geomagnetic warning.  "A weak slow moving CME associated with a
> disappearing solar filament on 23 August may have a glancing impact
> at Earth late on the UT day of the 26th or into 27th August.  Mildly
> elevated geomagnetic activity may occur following the impact.
> Another weak slow moving CME observed occurring towards the middle
> of the UT day on 24 August appears to be primarily eastward,
> although there is a chance it may also have a glancing impact at
> Earth during the 27th August, potentially resulting in mildly
> elevated geomagnetic activity."
> 
> Darrell Emerson, AA7FV wrote:
> 
> "I have a question about a possible 17m propagation anomaly between
> my location (AA7FV in Tucson AZ,  DM42pg, 32.3N 110.7 W) and the
> NCDXF beacon W6WX (CM97ae).  According to QRZ.com, W6WX is at a
> bearing of 301 degrees, and a distance of 1158 km from AA7FV.
> Sunset at W6WX is 02:49 UTC, and sunset at AA7FV is 01:58 UTC.
> 
> I have been using the program 'Faros' to look at the propagation
> times from various NCDXF beacons.  As I'm sure you know, the NCDXF
> beacons are time synchronized using GPS, and so by looking at the
> arrival times of transmissions from a given beacon, it is easily
> possible to distinguish between short path and long path
> propagation.  This is what the program Faros does.
> 
> As a check, here is data taken at the same time with the same setup
> on the beacon ZL6B, which shows no anomaly.  You can see that I was
> receiving the beacon from about 0h UTC until about 04:30 UTC.  The
> propagation delays (blue dots) line up precisely with the delay
> (about 39 ms) expected for short path propagation, which is marked
> by the horizontal dashed line labeled 'SP'.  No surprise here.  The
> expected long path delay would be nearly 100 ms, but there are no
> signals observed with that delay, during this time period."
> 
> Darrell sent graphics which I am unable to reproduce in this
> bulletin, but you could email him via his address on QRZ.com if you
> want copies.
> 
> I referred his quesion to Carl, K9LA, who responded:
> 
> "Thanks for those interesting plots from Faros.
> 
> ZL6B sunrise is around 1906 UTC, so I would have expected that you'd
> see him again later in the day (a bit after 1906 UTC).  But perhaps
> the MUF wasn't high enough at that time.  Or something else was going
> on.  Dropping out around 0430 UTC is understandable, as your sunet is
> around 0200 UTC and the MUF was slowly dropping until ZL6B (still in
> daylight) went away around 0430 UTC.
> 
> As for the W6WX results, being only 1158 km from you says a
> relatively high elevation angle would be required on the true great
> circle path.  And that says the MUF over that path would not likely
> be high enough for normal refraction at a high elevation angle on 18
> MHz (since we're just starting to come out of solar minimum).  So
> your comment about an unusual ionized cloud (or an enhanced area in
> the ionosphere) is a possible explanation.
> 
> The 20 msec or so delay suggests an off-great circle path from an
> enhanced area of ionization.  And my guess is that this area was
> south of you and W6WX as that puts it closer to the equatorial
> ionosphere, where more interesting short-term events happen than
> north of your location.  It's too bad that the azimuth arrival angle
> isn't measured."
> 
> If you're interested in some more Faros results, check out
> https://k9la.us/Aug17_Long_Path-Short_Path_Switching_on_15-Meters_Part_1.pdf
> and 
> https://k9la.us/Sep17_Long_Path-Short_Path_Switching_on_15-Meters_Part_2.pdf
> 
> By the way, Carl says he accidentally deleted an email from someone
> named Edgar in Toronto who had questions about VOACAP, and now he
> has no way to respond.  If you are Edgar, please contact K9LA.
> 
> Ken Brown, N4SO (EM50tk) in Alabama reported hearing the XE1FAS/B
> beacon on 28.171 MHz at 0542 UTC (12:42 AM local time) on August 26.
> "Just above the noise and then faded out."  The path distance was
> 1,001 miles.
> 
> Reader K6HPX has some fascinating antenna photos on his QRZ.com
> profile.  Check it out.
> 
> The latest from Dr. Tamitha Skov, WX6SWW:
> 
> https://youtu.be/jJgxa0SMojE
> 
> You can always find her new videos here:
> 
> https://www.spaceweatherwoman.com/forecasts/
> 
> For more information concerning shortwave 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/.
> 
> Instructions for starting or ending email distribution of ARRL
> bulletins are at http://arrl.org/bulletins .
> 
> Sunspot numbers for August 19 through 25, 2021 were 25, 14, 25, 16,
> 14, 29, and 29, with a mean of 21.7.  10.7 cm flux was 74.9, 77.7,
> 77.1, 77.1, 78.1, 80.9, and 83.6, with a mean of 78.5.  Estimated
> planetary A indices were 4, 5, 3, 3, 4, 5, and 9, with a mean of 4.7
> Middle latitude A index was 5, 6, 4, 4, 8, 5, and 8, with a mean of
> 5.7.
> NNNN
> /EX