Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 20, 1999 at 03:00 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 unsettled on September 19. Solar wind speed ranged between 375 and 498 km/sec. Solar flare activity was low. Solar flux was 149.3, the planetary A index was 10 (3-hour K indices: 2323 3322, Boulder K indices: 2323 3212). Region 8692 decayed further and will rotate over the west limb rotate. Region 8693 was quiet and stable and will rotate off the visible disk today. Region 8695 was quiet and stable. Region 8699 was mostly unchanged and will likely produce further C flares and perhaps even a minor M flare before rotating over the west limb late today. Region 8700 decayed slowly but could be capable of generating a minor M class flare. Region 8702 decayed into spotless plage. Region 8704 was quiet and stable but could be capable of minor M class flaring. Region 8705 decayed into spotless plage. New region 8706 rotated partly into view at the northeast limb. Flares and CMEs A total of 5 C flares were recorded on September 19 with region 8699 being the most active producing 4 of the events. The most intense flare of the day was an impulsive C9.6/1F event at 23:12 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 20. There is a slight chance of an impact from a CME observed on September 16. 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 8692 990907 1 S23W84 0060 HSX 8693 990907 1 N12W83 0010 AXX 8695 990910 1 N21W42 0010 HSX 8698 990911 S16W40 plage 8699 990911 6 N23W78 0170 ESO 8700 990912 26 N12W05 0070 DRI 8701 990913 N18W65 plage 8702 990916 N24W10 plage 8704 990917 7 S22E42 0180 CSO 8705 990918 S11E15 plage 8706 990919 1 N19E77 0080 HSX Total number of sunspots: 43 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 138.0 (1) 81.4 (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]