Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 24, 1999 at 03:25 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update September 1, 1999)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update September 1, 1999)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update September 1, 1999)] [Historical solar and geomagnetic data charts 1954-1999] Recent development The geomagnetic field was quiet to major storm on September 23. Solar wind speed ranged between 469 and 613 km/sec. Solar flare activity was low. Solar flux was 136.9, the planetary A index was 24 (3-hour Kp indices: 6631 2322, Boulder K indices: 5621 2222). Region 8700 decayed slowly and was quiet. Region 8702 once again decayed into spotless plage. Region 8704 was quiet and decayed slowly. Region 8706 was quiet and stable. Region 8707 was quiet and stable and appears to be spotless early on Septwember 24. Region 8708 was quiet and stable. Flares and CMEs Only 1 optically unaccounted C1.2 (at 00:28 UTC) flare was observed on September 23. The background x-ray flux is at the class B3 level. Coronal holes An isolated coronal hole near the solar equator will rotate into a geoeffective position late on September 24 and early on September 25. Forecast The geomagnetic field is expected to be quiet to unsettled on September 24-25. A coronal stream will likely arrive on September 27 or 28 and cause unsettled to active conditions. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally very poor. Coronal holes (1) Coronal mass M and X class flares (3) ejections (2) [Coronal hole indicator][CME indicator] [M and X class flare indicator] 1) Effects from a coronal hole could reach earth within the next 5 days. 2) Material from a CME is likely to impact earth within 96 hours. 3) There is a possibility of either M or X class flares within the next 48 hours. Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability. Active solar regions (Recent map) Solar Date Actual no. Location at region numbered sunspots midnight Area Classification Comment 8700 990912 6 N12W61 0010 BXO 8702 990916 N23W66 plage 8704 990917 8 S21W11 0100 CSO 8705 990918 S11W37 plage 8706 990919 5 N20E25 0110 CSO 8707 990922 1 S07W21 0000 AXX 8708 990922 8 S10E42 0040 CRO Total number of sunspots: 28 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 9807 114.0 66.6 65.5 (+3.0) 9808 136.0 92.2 67.8 (+2.3) 9809 138.3 92.9 69.5 (+1.7) 9810 117.2 55.5 70.5 (+1.0) 9811 140.1 74.0 73.0 (+2.5) 9812 150.1 81.9 77.9 (+4.9) 9901 140.6 62.0 82.6 (+4.7) 9902 141.9 66.3 84.6 (+2.0) 9903 126.3 68.8 (84.4 predicted, -0.2) 9904 117.2 63.9 (86.3 predicted, +1.9) 9905 148.4 106.4 (91.1 predicted, +4.8) 9906 169.8 137.4 9907 165.6 113.5 9908 170.7 93.7 9909 138.7 (1) 92.8 (2) 1) Running average based on the daily 20:00 UTC solar flux value at 2800 MHz.. 2) Unofficial, accumulated value. The official value is typically 25-40% less. This report has been prepared by Jan Alvestad. It is based partly on my own observations and interpretations, and partly on data from sources in solar links. Comments and suggestions are always welcome. ------------------------------------------------------------------------ [DX-Listeners' Club] [DX News] [StudyWeb]