Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 18, 1999 at 04:00 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 17. Solar wind speed ranged between 500 and 619 km/sec, generally decreasing slowly throughout the day. Solar flare activity was moderate. Solar flux was 157.5, the planetary A index was 15 (3-hour K indices: 3223 4422, Boulder K indices: 3223 3332). Region 8690 decayed slowly and will rotate off the visible disk early on September 19. Region 8692 decayed further and is unlikely to produce other than occasional C flares. Regions 8693 and 8695 decayed slowly and were quiet. Region 8699 decayed slowly and is likely to produce occasional C flares. Region 8700 has a distinct magnetic delta configuration in its southern part and has a fairly good chance of producing an M flare. Region 8702 decayed into spotless plage. New region 8703 emerged quickly in the northwest quadrant and has already rotated off the visible disk. New region 8704 rotated partly into view at the southeast limb. Flares and CMEs A total of 8 C flares (1 from region 8692, 1 from region 8699, 3 from region 8700 and 1 from region 8703) and 1 M flare were recorded on September 17. Region 8690 was the source of an impulsive M2.1 flare at 01:20 UTC. Region 8700 produced a C8.8/2F flare at 22:14 UTC. The background x-ray flux is at the class C1 level. Coronal holes An isolated coronal hole in the southern hemisphere was in a geoeffective position on September 15-16. A coronal hole in the northern hemipshere could move into a geoeffective position on September 21-22. Forecast The geomagnetic field is expected to be quiet to unsettled on September 18. Another coronal stream could arrive today or on September 19 and cause unsettled to minor storm conditions. 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 13 N16W74 0310 EAO 8692 990907 8 S25W53 0170 EAO 8693 990907 1 N12W56 0020 HSX 8695 990910 1 N21W16 0020 HSX 8697 990911 S20W84 plage 8698 990911 S16W14 plage 8699 990911 9 N22W52 0170 DSO 8700 990912 30 N13E20 0170 DAI beta-delta 8701 990913 N18W39 plage 8702 990916 N22E15 plage 8703 990917 1 N21W92 0000 AXX 8704 990917 1 S21E63 0070 HSX Total number of sunspots: 64 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 136.5 (1) 72.6 (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]