Solar Terrestrial Activity Report [Image] Last update September 20, 2001 at 04:20 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, 2001)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update September 1, 2001)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update September 1, 2001)] [Historical solar and geomagnetic data charts 1954-2001 (last update July 27, 2001)] Recent development The geomagnetic field was quiet to unsettled on September 19. Solar wind speed ranged between 370 and 481 km/sec. Solar flare activity was low. Solar flux was 199.8, the planetary A index was 8 (3-hour K indices: 3322 2231, Boulder K indices: 2321 2132). Region 9616 decayed significantly and has only a few spots left near the center of the region. Region 9617 decayed and could become spotless today or tomorrow. Region 9619 was quiet and stable. Regions 9620 and 9621 did not change significantly and could be a single region, region 9620 has a magnetic delta inside the main penumbra. Regions 9622 and 9623 were quiet and stable, both regions could soon become spotless. Region 9624 was quiet and stable. Region 9625 decayed quietly. Region 9626 developed slowly and was quiet. Region 9627 was quiet and stable. Region 9628 rotated fully into view revealing a region with at least minor M class flare potential. New region 9629 emerged quickly in the northeast quadrant. A new region trailing region 9628 is rotating into view at the southeast limb. Flares and CMEs A total of 5 C class events were observed on September 19. Region 9628 produced a C3.3 flare at 03:43 and a C7.5 flare at 18:52 UTC. Region 9621 generated a C6.0 flare at 08:11 UTC. An optically uncorrelated C7.2 long duration event was associated with a moderate type II radio sweep and a coronal mass ejection off the southwest limb, its origin was likely in region 9608 behind the limb. Region 9626 appears to have been the source of a type II radio sweep late in the day. A slow moving CME was first observed above the northeast limb at 02:18 UTC (on Sept. 20) in LASCO C3 images, this CME will likely appear as at least a partial halo CME when more images become available. The CME could be geoeffective and begin influencing the geomagnetic field on September 23. September 18: Region 9620 generated an M1.3/1F flare at 15:38 UTC and was the likely source of a partial halo CME observed in LASCO C3 images beginning at 19:42 UTC with a front first visible above most of the northern limbs and the north pole. This CME could be geoeffective and cause a minor disturbance on September 21 or 22. A full halo CME with a likely backsided origin was first observed above the southwest limb in LASCO C3 images at 21:18 UTC. The background x-ray flux is at the class C1-C2 level. Coronal holes No obvious coronal holes are currently approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to unsettled on September 20. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is 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 Location region numbered no. at Area Classification Comment sunspots midnight 9615 2001.09.08 N11W81 plage 9616 2001.09.11 20 S13W24 0190 FAO beta-gamma 9617 2001.09.12 11 N10W21 0020 BXO 9619 2001.09.13 5 N16W55 0030 DSO 9620 2001.09.16 6 N12E30 0210 CAO beta-gamma-delta 9621 2001.09.16 8 N14E36 0200 DAO 9622 2001.09.17 5 N13E08 0030 CSO 9623 2001.09.17 1 N22E18 0000 AXX 9624 2001.09.17 1 N03E42 0120 HSX 9625 2001.09.18 4 S30W24 0020 CRO 9626 2001.09.18 6 N26E25 0030 CRO 9627 2001.09.18 2 N04E58 0050 HAX 9628 2001.09.18 16 S18E64 0410 EKC beta-gamma 9629 2001.09.19 9 N26E38 0070 CAO Total number of sunspots: 94 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 2000.03 208.2 138.5 119.9 2000.04 184.2 125.5 120.8 cycle 23 sunspot max. 2000.07 202.3 170.1 119.7 2000.08 163.0 130.5 118.6 (-1.1) 2000.09 182.1 109.7 116.3 (-2.3) 2000.10 167.4 99.4 114.5 (-1.8) 2000.11 178.8 106.8 112.8 (-1.7) 2000.12 173.6 104.4 112.1 (-0.7) 2001.01 166.6 95.6 108.8 (-3.3) 2001.02 146.6 80.6 104.1 (-4.7) 2001.03 177.7 113.5 (103.8 predicted, -0.3) 2001.04 177.7 108.2 (104.1 predicted, +0.3) 2001.05 147.1 97.3 (102.6 predicted, -1.5) 2001.06 173.0 134.0 (99.8 predicted, -2.8) 2001.07 131.3 82.2 (98.0 predicted, -1.8) 2001.08 162.9 106.8 (98.5 predicted, +0.5) 2001.09 219.5 (1) 129.4 (2) (97.5 predicted, -1.0) 1) Running average based on the daily 20:00 UT solar flux value at 2800 MHz. 2) Unofficial, accumulated value based on the Boulder (SEC/NOAA) sunspot number. The official international sunspot number 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 noted in solar links. Comments and suggestions are always welcome. ------------------------------------------------------------------------ [DX-Listeners' Club] [DX News] [StudyWeb]