= NOW 18 WPM transition file follows = Sunspot numbers were lower again this week, with the average declining from 143.6 two weeks ago to 118.7 last week and now 68 this week. Average daily solar flux sank 8 points from 153.6 last week to 145.6. Six new sunspot groups emerged over the week, one on March 17, another March 18, three more on March 19, one more on March 21 and another on March 22. Predicted solar flux is 150, 145 and 145 on March 24 to 26, 150 on March 27 and 28, 145 and 150 on March 29 and 30, 138 on March 31 through April 1, then 136, 136 and 134 on April 2 to 4, 132 on April 5 to 7, 130 on April 8 and 9, then 132, 135, 138, and 140 on April 10 to 13, 142 on April 14 and 15, 143 on April 16, 140 on April 17 and 18, 142 on April 19 to 21, and 144 on April 22, 146 on April 23 and 24, 142 and 140 on April 25 and 26, 138 on April 27 and 28, and 136 on April 29 and 30. Predicted planetary A index is 35, 30, 20, 15 and 10 on March 24 to 28, 8 on March 29 and 30, then 18, 12, 12, 10 and 8 on March 31 through April 5, 5 on April 6 to 9, then 15, 12, 8 and 5 on April 10 to 13, 8 on April 14 and 15, then 12, 10, 5 and 5 on April 16 to 19, then geomagnetic unrest returns with 10, 36, 20, 10, 8 and 5 April 20 to 25, then 20, 18, 12, 12 and 10 on April 26 to 30. On Thursday, Spaceweather.com reported, The forecast did not call for this. During the early hours of March 23rd, a crack opened in Earths magnetic field, and stayed open for more than 8 hours. Solar wind poured through the gap to fuel a strong G3 class geomagnetic storm. Weekly Commentary on the Sun, the Magnetosphere, and the Earths Ionosphere, March 23, 2023, from F.K. Janda, OK1HH. If we were to assess solar activity in the last seven days by the number and size of sunspots, or by the number of energetic flares, it would not seem significant. Yet it was, but we only know that because of satellite observations. For example, NASAs SDO observatory recorded a dark plasma eruption at 0630 UTC on 17 March. The speed of the solar wind began to increase on 21 March. Far more noticeable was a large coronal hole in the southern hemisphere of the Sun near the central meridian. The assumption of a strong solar plasma flow from its borders pointed to a probable disturbance on March 24. But the flow was faster. We saw a really strong geomagnetic storm a day earlier, on March 23. During the morning hours, the concentration of free particles around the Earth began to rise rapidly, as a reliable precursor of the coming storm. The geomagnetic disturbance reached a planetary K index of 7 in the afternoon, so its intensity was rated G3. Earths ionosphere responded to the storm with an increase in MUF during 23 March. Since the disturbance should continue, albeit with less intensity, we expect initially below average shortwave propagation conditions and then a slow return to average. 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 ARLP012. Sunspot numbers were 84, 58, 35, 73, 75, 70, and 81, with a mean of 68. 10.7 cm flux was 135.4, 134.2, 140.3, 142.7, 156.1, 151.6, and 158.9, with a mean of 145.6. Estimated planetary A indices were 8, 7, 8, 10, 13, 8, and 17, with a mean of 10.6. Middle latitude A index was 6, 7, 6, 8, 10, 8, and 14, with a mean of 8.4. = END OF 18 WPM transition file <