Solar Terrestrial Activity Report [Image] Last update September 19, 2000 at 03:35 UTC. Minor update posted at 09:24 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 2, 2000)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update September 2, 2000)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update September 2, 2000)] [Historical solar and geomagnetic data charts 1954-2000 (last update August 10, 2000)] Recent development The geomagnetic field was unsettled to severe storm on September 18. Solar wind speed ranged between 566 and 922 km/sec. Solar flare activity was low. Solar flux was 203.8, the planetary A index was 45 (3-hour K indices: 7545 5533, Boulder K indices: 5544 5523). Region 9161 was quiet and stable. Region 9164 decayed into spotless plage. Region 9165 decayed slowly and was mostly quiet. Minor M class flares are still possible. Region 9166 developed slowly and has a weak magnetic delta configuration, the region is capable of M class flaring. Region 9167 developed slowly and could produce M class flares. Region 9168 developed slowly and was quiet. New region 9169 rotated into view at the northeast limb. This is a very large region which early on September 19 appears to have the largest areal coverage of any region so far in solar cycle 23. M and X class flares are possible. The separation between regions 9167 and 9169 is unclear and both regions could contribute to highly energetic flares. Comment added at 09:24 UTC on September 19: Region 9165 produced a major M5.1/1N flare at 08:26 UTC. There may have been a potentially geoeffective CME associated with this event. If there was another update will be posted later when images are available. Flares and CMEs A total of 9 C class events were recorded on September 18. Region 9167 produced a C2.3 flare at 02:49, a C3.3 flare at 12:31 and a C5.7 flare at 20:34 UTC. Region 9165 generated a C3.2 flare at 03:36 UTC while region 9166 managed a C3.2 flare at 05:29 and a C8.8/1F flare at 23:51 UTC. A partial halo CME covering the west limbs, the poles and parts of the east limbs was observed starting at 07:27 in LASCO C2 images, the origin is unclear and may have been on the back side of the sun. The background x-ray flux is at the class C1-C2 level. Coronal holes A coronal hole in the southern hemisphere was in a possibly geoeffective position on September 16-17. Forecast The geomagnetic field is expected to be quiet to active on September 19-20. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is 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 Location region numbered no. at Area Classification Comment sunspots midnight 9158 20000907 N31W74 plage 9161 20000911 7 N06W41 0040 DAO 9163 20000912 S17W88 plage 9164 20000913 S13W82 plage 9165 20000913 29 N14W40 0200 DAI beta-gamma 9166 20000914 34 S14E24 0570 EAI beta-gamma-delta 9167 20000916 12 N12E57 0320 DAO beta-gamma 9168 20000917 3 N09W07 0040 DSO 9169 20000918 9 N08E70 0870 EKI beta-gamma Total number of sunspots: 94 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 1999.07 165.6 113.5 94.3 (+1.2) 1999.08 170.7 93.7 97.5 (+3.2) 1999.09 135.7 71.5 102.3 (+4.8) 1999.10 164.8 116.7 107.8 (+5.5) 1999.11 191.5 133.2 110.9 (+3.1) 1999.12 169.8 84.6 111.0 (+0.1) 2000.01 158.1 90.1 112.8 (+1.8) 2000.02 174.1 112.9 116.6 (+3.8) 2000.03 208.2 138.5 (118.7 predicted, +2.1) 2000.04 184.2 125.3 (119.6 predicted, +0.9) 2000.05 184.9 120.8 (120.4 predicted, +0.8) 2000.06 179.8 124.9 (122.0 predicted, +1.6) 2000.07 202.3 169.1 (124.1 predicted, +2.1) 2000.08 163.0 130.6 2000.09 160.9 (1) 76.9 (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]