Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 17, 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 unsettled to major storm on September 16. Solar wind speed ranged between 549 and 665 km/sec mostly under the influence of a coronal stream. Solar flare activity was low. Solar flux was 158.2, the planetary A index was 32 (3-hour K indices: 3655 4433, Boulder K indices: 4555 2323). Region 8690 developed slowly and could produce further M class flares. Region 8692 decayed slowly and could produce further C flares. Regions 8693 and 8695 were quiet and stable. Region 8699 decayed slowly and is capable of C and minor M class flaring. Region 8700 developed slowly and has minor M class flaring potential. New region 8702 emerged in the northeast quadrant. An active region at the southeast limb will rotate into view today or tomorrow. An active region is developing in the southeast quadrant at a low latitude near the southeast limb. Flares and CMEs A total of 7 C flares were recorded on September 16. Region 8700 produced the largest event of the day, a C7.7 flare at 03:31 UTC. Other C flares were observed from region 8692 (1) and region 8699 (2). Region 8690 was the source of an impulsive M2.1 flare at 01:20 UTC on September 17. A huge filament eruption in the northwest quadrant began at 15:00 UTC on September 16. This resulted in a coronal mass ejection with most of the material observed over the north pole and the northwest limb. There is a possibility that a part of this CME could impact earth late on September 19 or early on the 20th. The background x-ray flux is at the class B7 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 active on September 17. Another coronal stream could arrive on September 18 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 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 8690 990906 23 N16W62 0440 EKI 8692 990907 16 S26W41 0170 ESO 8693 990907 1 N13W44 0030 HSX 8695 990910 3 N21W04 0030 CSO 8697 990911 S20W71 plage 8698 990911 S16W01 plage 8699 990911 13 N22W39 0220 ESO 8700 990912 25 N14E31 0140 EAO 8701 990913 N18W26 plage 8702 990916 2 N22E28 0000 BXO Total number of sunspots: 83 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 135.2 (1) 67.8 (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]