Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 19, 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 active on September 18. Solar wind speed ranged between 487 and 567 km/sec. Solar flare activity was low. Solar flux was 151.6, the planetary A index was 16 (3-hour K indices: 2334 4431, Boulder K indices: 2334 4421). Region 8690 was quiet and rotated over the west limb. Region 8692 decayed further and is unlikely to produce other than occasional C flares. Regions 8693 and 8695 were quiet and stable. Region 8699 decayed slowly and is likely to produce occasional C flares. Region 8700 decayed slowly but could still produce an isolated minor M class flare. Region 8702 reemerged with a few spots but appears to have become spotless again early on September 19. Region 8704 was quiet and stable but could be capable of minor M class flaring. New region 8705 emerged in the southeast quadrant. Flares and CMEs Flare frequency and intensity decreased on September 18 as 5 C flares were recorded. Region 8699 produced 2 of them while region 8700 managed only one C flare. The most energetic flare of the day was an optically unaccounted C2.9 event at 16:05 UTC. The background x-ray flux is at the class B7 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 19 with a possibility of isolated active intervals. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally 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 8690 990906 7 N16W87 0110 DSO 8692 990907 5 S25W69 0110 CSO 8693 990907 1 N12W71 0030 HSX 8695 990910 2 N21W31 0020 CSO 8698 990911 S16W27 plage 8699 990911 6 N22W65 0160 DSO 8700 990912 31 N13E07 0110 DSI 8701 990913 N18W52 plage 8702 990916 3 N24E03 0010 BXO 8704 990917 5 S21E52 0110 CSO 8705 990918 2 S11E28 0010 AXX Total number of sunspots: 62 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 (85.0 predicted, +0.4) 9904 117.2 63.9 (88.0 predicted, +3.0) 9905 148.4 106.4 (93.4 predicted, +5.4) 9906 169.8 137.4 9907 165.6 113.5 9908 170.7 93.7 9909 137.4 (1) 77.6 (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]