Solar Terrestrial Activity Report [Image] Last update September 21, 2001 at 04:00 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 on September 20. Solar wind speed ranged between 302 and 382 km/sec. Solar wind parameters do not currently indicate the approach of any significant disturbance. Solar flare activity was moderate. Solar flux was 226.8, the planetary A index was 5 (3-hour K indices: 1112 2222, Boulder K indices: 1113 3112). Region 9616 developed new spots in the trailing section and was otherwise mostly unchanged. Region 9619 was quiet and stable. Regions 9620 and 9621 did not change significantly and could be a single region, region 9620 still has a magnetic delta inside the main penumbra. Region 9622 developed slowly and was quiet. Region 9623 decayed slowly and could become spotless today. Region 9624 was quiet and stable, as were regions 9625, 9626 and 9627. Region 9628 developed slowly and has major flare potential. Region 9629 was mostly unchanged and quiet. New region 9630 emerged in the northwest quadrant. New region 9631 emerged quickly in the northwest quadrant near the central meridian. New region 9632 rotated into view at the southeast limb and has minor M class flaring potential. An interesting region is approaching the northeast limb. Flares and CMEs A total of 6 C and 1 M class events were observed on September 20. Region 9628 produced a C7.8 flare at 05:10 and a C3.8 flare at 18:51 UTC. Region 9631 was the source of an M1.5 flare at 18:17 UTC. A full halo CME was observed in LASCO C3 images beginning at 16:42 UTC, most of the material was observed over the east limbs. Its source is currently unknown (due to the lack of LASCO EIT images). September 19: 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 and later became a partial halo CME. The CME is probably not geoeffective. 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 21-22. There is a chance (20-30%) of CME related disturbances arriving today and tomorrow. If they do impact Earth they will likely cause only mild geomagnetic activity. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is fair. 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 9616 2001.09.11 18 S12W37 0180 FAO beta-gamma 9617 2001.09.12 N10W34 plage 9619 2001.09.13 3 N17W67 0020 BXO 9620 2001.09.16 9 N12E17 0210 DAO beta-gamma-delta 9621 2001.09.16 10 N15E22 0180 DAO 9622 2001.09.17 14 N13W05 0060 DAO 9623 2001.09.17 1 N21E04 0000 AXX 9624 2001.09.17 1 N03E29 0100 HSX 9625 2001.09.18 2 S28W36 0010 BXO 9626 2001.09.18 7 N26E14 0040 BXO 9627 2001.09.18 3 N04E43 0040 CSO 9628 2001.09.18 33 S18E51 0800 FKC beta-gamma 9629 2001.09.19 7 N26E23 0060 DSO 9630 2001.09.20 3 N27W36 0010 CSO 9631 2001.09.20 9 N08W15 0060 DAO 9632 2001.09.20 6 S18E76 0390 EKO Total number of sunspots: 126 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) 2001.09 219.8 (1) 138.6 (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]