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LATEST K7RA HF Propagation Bulletin


From Tad Cook, K7RA
Seattle, Washington, USA
To all Amateur Radio Operators


Friday, August 17, 2018 23:24 GMT


Australia's Space Weather Services issued a Geomagnetic Disturbance Warning at 0022 UTC on August 16: "Geomagnetic activity is expected to be at Quiet to Active levels due to coronal hole effects. A period of significant southward Bz component could produce isolated Minor Storm levels." What is the Bz component? It is a component of the interplanetary magnetic field, or IMF. The site http://pluto.space.swri.edu/IMAGE/glossary/IMF.html explains: "The IMF is a vector quantity with three directional components, two of which (Bx and By) are oriented parallel to the ecliptic. The third component--Bz--is perpendicular to the ecliptic and is created by waves and other disturbances in the solar wind. When the IMF and geomagnetic field lines are oriented opposite or 'antiparallel' to each other, they can 'merge' or 'reconnect,' resulting in the transfer of energy, mass, and momentum from the solar wind flow to magnetosphere. The strongest coupling --with the most dramatic magnetospheric effects-- occurs when the Bz component is oriented southward." A high-speed solar wind stream is expected to emerge from the coronal hole. Solar activity is still very weak. The previous propagation forecast bulletin (ARLP032) reported two days with a sunspot number of 11, on each day, for August 2-8, yielding the average daily sunspot number for the week at 1.6. This week's average was 3.4, based on a sunspot number of 12 on both August 14 and 15. That activity continued on Thursday, August 16, also with a daily sunspot number of 12. Average solar flux went in the other direction, changing to 68.7 from 69.7 in the previous week. Geomagnetic indicators were higher, with average daily planetary A index shifting from 5.7 to 6.9, and mid-latitude A index from 6.9 to 7.3. Activity is weak and should get weaker, at least until two years from now in 2020 when we will probably reach the bottom of Solar Cycle 24. Predicted solar flux (August 16 forecast from USAF via NOAA) is 69 on August 17-23, 70 on August 24 through September 5, 68 on September 6-18, and 70 on September 19-30. Predicted planetary A index from the same forecast is 10 on August 17, 5 on August 18-20, 15 on August 21-22, 10 on August 23, 5 on August 24 through September 2, then 12, 8, 5, 5, 10, 8 and 8 on September 3-9, then 5 on September 10-11, then 12, 15, 8, 5, 15 and 12 on September 12-17, 5 on September 18-28, 8 on September 29 and 12 on September 30. F.K. Janda, OK1HH sends us his Geomagnetic Activity Forecast for the period August 17 to September 12, 2018. Geomagnetic field will be: Quiet on August 22-24, 31, September 5, 9 Quiet to unsettled on August 18, 25, 30, September 1-2, 4, 6 Quiet to active on August 17, 19, 26-29, September 3, 8 Unsettled to active on August 21, September 7, 10, 12 Active to disturbed on August 20, September 11 Solar wind will intensify on August (16-19), 20-22, 28-30, September 10-12 Remarks: - Parenthesis means lower probability of activity enhancement. - Reliability of predictions remains low. Interesting article about cosmic rays can be found at, https://bit.ly/2KTiMcH . This article was written by Dr. Tony Phillips of Spaceweather.com. On Tuesday, August 14, Dr. Tamitha Skov sent this message and video: "Dear Tad, "Another quick note to let you know my latest 'forecast shortie' is up for viewing on You Tube. However, I can report some good news since I shot the forecast. A new, albeit tiny active region is emerging on the Earth-facing Sun and is growing fast! This means both solar flux and amateur radio propagation might be getting a much needed boost over the next couple of days. I will be sure to keep you updated on how this new region is progressing when I shoot my full length forecast in the next couple of days. Again, a huge *THANK YOU* to the Patreon members during this pre-launch phase, who are making these 'forecast shorties' possible!" https://youtu.be/fl325AOjItM Dr. Skov mentioned the Parker Solar Probe, which launched August 12: https://youtu.be/AzDa9bJykBY https://www.nasa.gov/content/goddard/parker-solar-probe If you would like to make a comment or have a tip for our readers, email the author at, k7ra@arrl.net .