Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 21, 1999 at 03:10 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 unsettled on September 20. Solar wind speed ranged between 357 and 416 km/sec. Solar flare activity was low. Solar flux was 145.0, the planetary A index was 10 (3-hour Kp indices: 2223 3233, Boulder K indices: 2223 3233). Region 8695 was quiet and stable. Region 8699 produced several C flares while rotating over the west limb. Region 8700 decayed further and appears uncapable of generating other than occasional C flares. Region 8704 was quiet and stable. Region 8706 was quiet but is likely to produce occasional C class flares. Flares and CMEs A total of 7 C flares were recorded on September 20. Only 1 was attributed to region 8700 with most if not all of the remaining events occurring in region 8699 as observed in LASCO EIT movies. A filament eruption over the central meridian in the southern hemisphere started at 03:48 UTC. No CME was obvious below the south pole or the limbs in the LASCO C2 movie. There is a small chance of terrestrial effects from this eruption on September 23. The background x-ray flux is at the class B5 level. Coronal holes No obvious coronal holes are approaching a geoeffective position. Forecast The geomagnetic field is expected to be quiet to unsettled on September 21-22. On September 23 there is a minor chance of a weak CME impact related to a filament eruption on September 20. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally poor and improving. 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 8695 990910 1 N21W56 0010 AXX 8698 990911 S16W53 plage 8699 990911 1 N24W88 0060 HSX 8700 990912 18 N12W19 0050 DSO 8701 990913 N18W78 plage 8702 990916 N24W23 plage 8704 990917 6 S22E28 0110 ESO 8705 990918 S11E02 plage 8706 990919 2 N20E66 0120 CSO 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 138.3 (1) 84.0 (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]