Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 23, 1999 at 03:15 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 22. Solar wind speed ranged between 348 and 632 km/sec. A solar wind shock was observed at ACE at 11:45 UTC with an abrupt increase in wind speed from 360 to 460 km/sec. The interplanetary magnetic field swung very strongly southwards for a few minutes initially, then swung strongly to very strongly northwards until approximately 18:30 UTC. From then until 21:30 UTC the IMF had a sustained period of strong to very strong southward magnetic orientation. This resulted in major to very severe storming 21-00 UTC with the planetary A index for that interval reaching 143. The source of the disturbance is likely a coronal mass ejection associated with a filament eruption observed early on September 20. Solar flare activity was low. Solar flux was 140.4, the planetary A index was 44 (3-hour Kp indices: 1123 3333, Boulder K indices: 2123 3233). Region 8695 decayed into spotless plage. Region 8700 was mostly quiet and stable. Region 8702 was quiet and stable. Region 8704 was quiet and stable and remains capable of producing C flares. Region 8706 could generate further C class flares. New region 8707 emerged in the the southwest hemisphere near the central meridian. New region 8708 emerged quickly near the southeast limb. Flares and CMEs A total of 3 C flares were recorded on September 22. Regions 8700, 8706 and 8708 produced 1 C flare each with the flare from region 8706 being the largest event of the day. It occurred at 13:40 UTC and was a C5.2/1F event. The background x-ray flux is at the class B3 level. Coronal holes A fairly small coronal hole near the solar equator will rotate into a geoeffective position on September 25. Forecast The geomagnetic field is expected to be unsettled to major storm on September 23 and quiet to unsettled on September 24. A coronal stream could arrive on September 28 and cause unsettled to active conditions. 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 no. Location at region numbered sunspots midnight Area Classification Comment 8695 990910 N22W83 plage 8698 990911 S16W79 plage 8700 990912 13 N13W47 0040 CRO 8702 990916 2 N23W53 0000 BXO 8704 990917 14 S22E01 0120 CSO 8705 990918 S11W24 plage 8706 990919 2 N19E38 0090 HSX 8707 990922 3 S07W08 0000 BXO 8708 990922 9 S09E55 0040 CRO Total number of sunspots: 43 Monthly solar data Month Average International Smoothed solar flux sunspot number sunspot number 9807 114.0 66.6 65.5 (+3.0) 9808 136.0 92.2 67.8 (+2.3) 9809 138.3 92.9 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) (84.4 9903 126.3 68.8 predicted, -0.2) (86.3 9904 117.2 63.9 predicted, +1.9) (91.1 9905 148.4 106.4 predicted, +4.8) 9906 169.8 137.4 9907 165.6 113.5 9908 170.7 93.7 9909 138.8 (1) 90.2 (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]