Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 22, 1999 at 02:30 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 21. Solar wind speed ranged between 343 and 418 km/sec. The interplanetary magnetic field strengthened and swung moderately strongly southwards towards the end of the day. Solar flare activity was low. Solar flux was 146.8, the planetary A index was 10 (3-hour Kp indices: 1123 3333, Boulder K indices: 2123 3233). Region 8695 was quiet and stable, the region will likely become spotless today. Region 8700 was quiet and stable. Region 8702 once again reemerged with a few spots. Region 8704 could produce further C flares. Region 8706 was unstable early in the day and became quiet and stable following the C9 flare. Flares and CMEs A total of 4 C flares were recorded on September 21. An erupting prominence near region 8699 at the west limb was the source of a C5.2 event at 03:32 UTC. It was accompanied by a weak type II sweep and a CME off the northwest limb. Region 8706 generated a C9.4 flare at 03:52 UTC. A weak coronal mass ejection over the east limb was observed. September 20: A filament eruption over the central meridian in the southern hemisphere started at 03:48 UTC. A weak full halo CME was observed in LASCO C3 images. A terrestrial impact is likely on September 23 or early on September 24. The background x-ray flux is at the class B4 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 quiet to unsettled on September 22, possibly with isolated active intervals. On September 23 or early on September 24 a weak CME will likely impact the earth resulting in unsettled to active conditions with a fair chance of minor storm intervals. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally fair to 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 8695 990910 1 N22W70 0000 AXX 8698 990911 S16W66 plage 8700 990912 16 N13W33 0040 CSO 8702 990916 3 N24W40 0000 BXO 8704 990917 9 S22E16 0130 ESO 8705 990918 S11W11 plage 8706 990919 3 N20E53 0110 CSO Total number of sunspots: 32 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 (84.4 predicted, -0.2) 9904 117.2 63.9 (86.3 predicted, +1.9) 9905 148.4 106.4 (91.1 predicted, +4.8) 9906 169.8 137.4 9907 165.6 113.5 9908 170.7 93.7 9909 138.7 (1) 86.7 (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]