Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 16, 1999 at 03:40 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 severe storm on September 15. Solar wind speed ranged between 442 and 746 km/sec. A solar wind shock was observed at ACE at 0711 UTC. Solar wind speed increased abruptly from 500 to 600 km/sec and the interplanetary magnetic field strengthened considerably and swung strongly southwards. This caused minor storming at low and middle latitudes and severe to extremely severe storming at high latitudes. The source of the disturbance was likely a partial halo CME observed at 09h UTC on September 13. Another solar wind shock (a weak one) was observed at 19:40 UTC at SOHO. This didn't cause any immediate increase in geomagnetic activity, however, the interplanetary magnetic field has again become stronger and swung southwards early on September 16. Solar flare activity was low. Solar flux was 154.9, the planetary A index was 32 (3-hour K indices: 4357 4332, Boulder K indices: 4455 3221). Region 8690 developed slowly and remains capable of producing C flares and occasional minor M flares. Region 8692 decayed slowly and could produce occasional C flares. Regions 8693 and 8695 were quiet and stable. Region 8699 was mostly unchanged and has minor M class flaring potential. Region 8700 developed a magnetic delta configuration and should be capable of producing a minor M class flare. A large region is approaching the southeast limb and should rotate into view over the next couple of days. Flares and CMEs A total of 6 C flares were recorded on September 15 with region 8699 producing 1 and region 8700 the source of 2 of the flares. The background x-ray flux is at the class B6 level. Coronal holes A coronal hole in the northern hemisphere was in a geoeffective position on September 12-13. Another isolated coronal hole in the southern hemisphere was in a geoeffective position on September 15-16. Forecast The geomagnetic field is expected to be unsettled to major storm on September 16 and quiet to active on September 17. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally very poor to useless. 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 Location region numbered no. at Area Classification Comment sunspots midnight 8690 990906 30 N15W48 0300 EKI 8692 990907 19 S26W27 0160 CSO 8693 990907 2 N13W29 0030 CSO 8695 990910 3 N22E08 0040 CSO 8697 990911 S20W58 plage 8698 990911 S16E12 plage 8699 990911 23 N22W25 0220 EAO 8700 990912 18 N14E45 0130 EAO beta-gamma-delta 8701 990913 N18W13 plage Total number of sunspots: 95 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 133.7 (1) 62.7 (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]