Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update August 31, 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 August 2, 1999)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update August 2, 1999)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update August 2, 1999)] [Historical solar and geomagnetic data charts 1954-1999] Recent development The geomagnetic field was quiet to minor storm on August 30. Solar wind speed ranged between 480 and 597 km/sec. A disturbance was observed at ACE near 06:30 UTC with the interplanetary magnetic field swinging weakly southwards for approximately 3 hours. The IMF was moderately strongly southwards between 13h and 17:30 UTC. No solar wind shock was observed, however, solar wind density was elevated between 05:30 and 12h UTC. Solar flare activity was moderate. Solar flux was 198.1, the planetary A index was 20 (3-hour K indices: 2255 3333, Boulder K indices: 2245 3322). Region 8673 did not change significantly and produced several sub flares and a C flare. Region 8674 decayed but is still a complex region where the magnetic polarities are intermixed throughout most of the region. A weak magnetic delta is still present in the trailing end of the region. Further M flares are possible and there is a slight chance of an X flare. Region 8675 decayed slowly and was quiet. Region 8676 decayed slowly and produced several sub flares. Regions 8677 and 8679 were quiet and stable. Region 8681 was mostly unchanged and is likely to produce further C flares. Isolated M flares are possible. Region 8682 was quiet and stable. New regions 8683 and 8684 emerged in the southeast quadrant. Flares and CMEs A total of 7 C flares (1 from region 8673, 1 from region 8674 and 2 from region 8681) and 1 M flare was recorded on August 30. Region 8674 produced the 2 most significant events of the day, first a C9.4/1N at 14:45 UTC, then an M3.8/2B moderate duration event at 18:05 UTC. The latter event was associated with a moderately strong type II sweep. Although this is normally associated with a coronal mass ejection, no obvious CME has been observed in LASCO images. August 28: Region 8674 was the source of an X1.1 moderate duration major flare which peaked at 18:05 UTC. It was accompanied by a strong type II sweep and a large coronal mass ejection. At least a partial halo CME was observed in LASCO images with the densest part of the CME below the south pole. A terrestrial impact is likely sometime from early on August 31 to early on September 1 but is not likely to create a disturbance beyond the active to minor storm levels. The background x-ray flux is at the class C1 level. Coronal holes No obvious coronal holes are currently approaching geoeffective positions. Forecast The geomagnetic field is expected to be unsettled to minor storm on August 31 and September 1. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is poor to very 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 Location region numbered no. at Area Classification Comment sunspots midnight 8673 990819 2 S19W64 0270 HHX 8674 990820 45 S24W51 0480 FAI beta-gamma-delta 8675 990824 21 N19E01 0170 DSI 8676 990824 4 N27W04 0010 BXO 8677 990825 3 N07E07 0070 CSO 8679 990826 4 S33E09 0010 BXO 8681 990828 28 N21W17 0280 DAI beta-gamma 8682 990829 2 N18E51 0020 CSO 8683 990830 1 S10E37 0000 AXX 8684 990830 2 S12E49 0000 AXX Total number of sunspots: 112 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 62.4 82.6 (+4.7) 9902 141.9 66.1 (84.9 predicted, +2.3) 9903 126.3 69.1 (86.4 predicted, +1.5) 9904 117.2 63.9 (90.0 predicted, +3.6) 9905 148.4 106.3 9906 169.8 137.4 9907 165.6 113.5 9908 170.4 (1) 129.9 (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]