Solar Terrestrial Activity Report [Image] Last update April 26, 2000 at 02:45 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update April 2, 2000)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2000)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update April 2, 2000)] [Historical solar and geomagnetic data charts 1954-2000 (last update April 12, 2000)] Recent development The geomagnetic field was quiet to unsettled on April 25. Solar wind speed ranged between 417 and 571 km/sec. Solar flare activity was low. Solar flux was 202.5, the planetary A index was 6 (3-hour K indices: 3012 2232, Boulder K indices: 2112 2222). Region 8962 was quiet and stable and will rotate over the west limb today. Region 8963 decayed into spotless plage. Region 8965 was quiet and stable, as was region 8966. Region 8967 will likley continue to produce C flares and has a chance of generating a minor M class flare. Region 8968 was quiet and stable. Region 8969 decayed and could become spotless today. Region 8970 developed slowly but remained mostly quiet. The region is large and could produce a major flare. Region 8971 is slowly decaying but could still generate an M class flare. Region 8972 was mostly unchanged. Further C class flares are likely and a minor M class flare is a possibility. Region 8973 did not change significantly and was quiet. Region 8974 was quiet and stable. Flares and CMEs A total of 7 C flares were recorded on April 25. Region 8967 produced a C1.6/1F flare at 18:04 UTC. Region 8970 was the source of a C1.3 flare at 03:35 UTC. Region 8972 generated a C1.8 flare at 09:29 and a C1.6 flare at 18:48 UTC. The background x-ray flux is at the class B6 level. Coronal holes Small coronal holes in the northern hemisphere could rotate into geoeffective positions on April 29-30. Forecast The geomagnetic field is expected to be quiet to unsettled on April 26. 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 no. Location at region numbered sunspots midnight Area Classification Comment 8962 20000413 1 N25W78 0000 AXX 8963 20000413 N17W83 plage 8965 20000417 8 S16W39 0040 DAO 8966 20000418 2 S12W29 0000 BXO 8967 20000419 14 N23W16 0130 FAO beta-gamma 8968 20000419 6 S13W52 0070 DSO 8969 20000420 1 N12W06 0000 AXX 8970 20000420 41 S15E18 1080 EKC beta-gamma 8971 20000421 24 N18E16 0830 FKO beta-gamma 8972 20000421 11 N34W47 0240 EAO 8973 20000422 10 N22W52 0130 DAO 8974 20000423 1 S12W63 0000 AXX 8975 20000423 S25E24 plage Total number of sunspots: 119 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 1999.03 126.3 69.1 83.8 (-0.8) 1999.04 117.2 63.9 85.4 (+1.6) 1999.05 148.4 106.3 90.4 (+5.0) 1999.06 169.8 137.7 93.0 (+2.6) 1999.07 165.6 113.5 94.4 (+1.4) 1999.08 170.7 93.7 97.5 (+3.1) 1999.09 135.7 71.5 102.3 (+4.8) 1999.10 164.8 116.4 (108.6 predicted, +6.3) 1999.11 191.5 132.7 (112.3 predicted, +3.7) 1999.12 169.8 86.4 (111.9 predicted, -0.4) 2000.01 158.1 90.2 (112.7 predicted, +0.8) 2000.02 174.1 112.3 (116.2 predicted, +3.5) 2000.03 208.2 138.2 2000.04 184.9 (1) 164.1 (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]