Solar Terrestrial Activity Report [Image] Last update September 25, 2000 at 03:45 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 quiet to active on September 24. Solar wind speed ranged between 369 and 588 km/sec. A weak solar wind shock was observed at ACE at 15:20 UTC. The interplanetary magnetic field immediately swung moderately southwards and was weakly to moderately southwards for the remainder of the day. Solar flare activity was moderate. Solar flux was 224.5, the planetary A index was 10 (3-hour K indices: 1012 3343, Boulder K indices: 1111 2343). Region 9166 developed a weak magnetic delta configuration and became the most active region. Further M class flares are possible. Region 9167 decayed slowly and was quiet. Region 9169 increased its spot count (according to SEC/NOAA) to 119, again a record for solar cycle 23. Early on Sept.25 it is obvious the region has lost quite a bit of its penumbral coverage. Still the region is large and complex and could produce a major flare at any time. Region 9170 was mostly unchanged and quiet. Region 9171 was quiet and stable. New region 9172 rotated into view at the northeast limb. New region 9173 rotated into view at the southeast limb. Flares and CMEs A total of 6 C and 1 M class events were recorded on September 24. Region 9166 produced an M4.3/2N flare at 03:38, a C3.0 flare at 07:11, a C2.2 flare at 13:21 and a C3.6 flare at 14:08 UTC. Region 9169 managed a C1.8 flare at 13:17 UTC. Region 9166 was the source of an M3.4 flare at 00:53 on September 24. An M1.8 flare was observed at 02:15 UTC, possibly originating from region 9169. September 23: Region 9169 produced a C8.6/1F flare at 21:42 UTC. This event may have been associated with a weak halo CME, at least there was material movement in LASCO C2 images at both east and west limbs within an hour after the end of the flare. The background x-ray flux is at the class C1-C2 level. Coronal holes No obvious coronal holes are approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to active on September 25. There is a possibility of a fairly weak CME impact late on September 26 or early on the 27. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is 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 9166 20000914 38 S11W56 0340 EAI beta-gamma-delta 9167 20000916 6 N15W28 0080 CSO 9168 20000917 N09W85 plage 9169 20000918 119 N11W09 1930 FKC beta-gamma-delta 9170 20000921 17 S05W14 0100 DAO 9171 20000922 3 S15E47 0080 DSO 9172 20000923 1 N12E70 0050 HSX 9173 20000923 1 S14E72 0030 HSX Total number of sunspots: 185 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 2000.09 175.9 (1) 117.8 (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]