[South Florida DX Association] ARLP006 Propagation de K7RA

[Bill Marx]

 SB PROP @ ARL $ARLP006
> ARLP006 Propagation de K7RA
> 
> ZCZC AP06
> QST de W1AW  
> Propagation Forecast Bulletin 6  ARLP006
> From Tad Cook, K7RA
> Seattle, WA  February 11, 2005
> To all radio amateurs 
> 
> SB PROP ARL ARLP006
> ARLP006 Propagation de K7RA
> 
> All solar activity indicators rose this week, though not by much.
> Average daily sunspot number for the week rose 4.4 points to 41.3,
> average daily solar flux was up 11.6 points to 85.1, and average
> planetary A index rose 4 points to 15.1. Average daily mid-latitude
> A index rose 2.2 points to 10.6.
> 
> Monday through Wednesday, February 7-9 had unsettled to active
> geomagnetic activity with Tuesday the most disturbed day. The
> planetary A index was 34 that day and mid-latitude A index was 27.
> At the 0300z February 8 reading, the planetary K index reached a
> high of 6, and the highest reading for Alaska's college K index came
> at 1800z that day when it reached a very high value of 8. There was
> a K index of 7 on the previous day, and the college A index for
> February 7-10 was 50, 71, 45 and 30, all high values.
> 
> This is why Alaskan operators oftentimes report such poor HF
> conditions during periods when the rest of the United States hardly
> notices. For instance, between 1200-1500z on February 8, the Alaska
> K index readings were 6, 6, and 8, indicating a severe geomagnetic
> storm. But the mid-latitude K index, which affects most of the rest
> of us was only 2, 3 and 3, quite moderate numbers. Of course for the
> rest of us, a high latitude path (such as the one to Europe from
> Seattle) would also be affected, even though each end of the path is
> at a more moderate latitude.
> 
> The college A and K index is measured at Fairbanks, Alaska, and the
> mid-latitude indices that we use are from Fredericksburg, Virginia.
> The planetary K and A index is the mean-standardized index from 13
> geomagnetic observatories between 44 and 60 degrees northern or
> southern latitude.
> 
> That single A index for the day is calculated from the eight K index
> readings, and the scales are quite different, the K index being
> quasi-logarithmic. A single point change in the K index is quite
> significant, but a several point change in the A index is not. A day
> with all eight K index readings of 2 would yield an A index for the
> day of 7, but all-day K index of 3 would produce an A of 15, and K
> of 4 all day would yield an A index of 27. You can check the
> relationship between the A and K readings on NOAA's National
> Geophysical Data Center site at,
> http://www.ngdc.noaa.gov/stp/GEOMAG/kp_ap.html.
> 
> A week-long graph showing Boulder (another mid-latitude
> observatory), Fredericksburg, planetary and college K index is at
> http://www.sec.noaa.gov/alerts/k-index.html. Notice from the graphs
> that the Boulder measurement is often slightly higher (at least it
> was in the week prior to this bulletin) than the Fredericksburg
> values. There is only a two-degree difference in latitude, Boulder
> being at 40 degrees north, and Fredericksburg at 38 degrees north.
> 
> The higher A and K numbers this week were caused by a robust solar
> wind stream. The Interplanetary Magnetic Field pointed south, so the
> earth was vulnerable to these particles. When the IMF points north,
> the earth is shielded, and it didn't point north until February 10,
> a quiet day.
> 
> Last week this bulletin said that solar flux values should rise to
> 130 by February 7, and stay there for about a week. This was because
> of the return of sunspot 720, which was quite large the last time it
> faced earth. When 720 returned a few days after the bulletin, it was
> much smaller than before. Currently solar flux is expected to stay
> around 115 for February 11-12, then drop a few points for the next
> few days. Solar flux could drop below 100 around February 19, but
> the further out we look, the prediction becomes less meaningful.
> 
> Roger Bonuchi, AC9Y of Plainfield, Illinois sent an email this week
> asking about GOES Solar X-Ray Flux as shown at,
> http://www.sec.noaa.gov/today.html#xray. He wonders if this relates
> to the 10.7 cm solar flux we report in this bulletin. They actually
> are measurements of electromagnetic radiation in different parts of
> the spectrum. X-rays have wavelengths shorter than ultraviolet
> light. 10.7 cm solar flux is at a much lower frequency, around 2.8
> GHz.
> 
> See the relative positions of x-rays, light waves and radio waves at
> a physics study aid at,
> http://www.plus2physics.com/electrons_and_photons/study_material.asp?cha
> pter=4.
> 
> 10.7 cm solar flux correlates to some degree with sunspots, and
> typically the higher solar flux or sunspot numbers result in a
> higher MUF, or Maximum Usable Frequency. If you use a propagation
> program such as W6ELprop (free at http://www.qsl.net/w6elprop/),
> over most paths the MUF will go higher when the sunspot numbers or
> solar flux are higher.
> 
> X-rays are correlated with events such as coronal mass ejections or
> solar flares, and the measurements shown in the graph that Roger
> sent are done by the GOES satellite. You'll notice on that same page
> there is a link to the D-region absorption prediction at
> http://www.sec.noaa.gov/rt_plots/dregion.html, which should show
> greater absorption when the x-ray flux is higher.
> 
> Allen Robbins, W7AM of Salem, Oregon asked about the scales heard on
> the WWV geophysical alerts. You can see the text of the latest WWV
> broadcast alert at http://sec.noaa.gov/ftpdir/latest/wwv.txt. A
> couple of web pages that explain the numbers and scales for radio
> blackouts, solar radiation storms and geomagnetic storms are at,
> http://www.sel.noaa.gov/Data/info/WWVdoc.html and
> http://www.sel.noaa.gov/NOAAscales/index.html.
> 
> If you would like to comment or have a tip, email the author at,
> k7ra at arrl.net.
> 
> For more information concerning propagation and an explanation of
> the numbers used in this bulletin see the ARRL Technical Information
> Service propagation page at,
> http://www.arrl.org/tis/info/propagation.html.
> 
> Sunspot numbers for February 3 through 9 were 23, 22, 22, 47, 62, 53
> and 60 with a mean of 41.3. 10.7 cm flux was 83, 82.1, 94.6, 97,
> 103.1, 108.2 and 108.6, with a mean of 96.7. Estimated planetary A
> indices were 8, 3, 4, 9, 23, 34 and 25 with a mean of 15.1.
> Estimated mid-latitude A indices were 5, 2, 1, 6, 19, 27 and 14,
> with a mean of 10.6.
> NNNN
> /EX