Solar Terrestrial Activity Report [Image] Last update April 27, 2000 at 03:40 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 on April 26. Solar wind speed ranged between 384 and 480 km/sec. Solar flare activity was low. Solar flux was 189.9, the planetary A index was 4 (3-hour K indices: 1012 1222, Boulder K indices: 0011 1222). Region 8965 was mostly quiet and stable. Region 8966 developed slowly and was quiet. Region 8967 was mostly quiet and stable but could produce occasional C flares. Region 8968 was quiet and stable. Region 8969 was quiet and stable. Region 8970 did not change significantly and could still produce a major flare. Region 8971 was mostly unchanged as well and could generate an M class flare. Regions 8972 and 8973 decayed slowly and were quiet. Region 8974 decayed into spotless plage. Flares and CMEs A total of 10 C flares were recorded on April 26. Region 8965 generated a C1.6 flare at 15:29 UTC. Region 8967 was the source of a C2.2 flare at 19:05 and a C1.0 flare at 21:54 UTC. Region 8970 produced a C2.8 flare at 07:44, a C6.3 flare at 09:23 and a C1.4 flare at 12:45 UTC. The background x-ray flux is at the class B5 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 27-29. 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 no. Location at region numbered sunspots midnight Area Classification Comment 8965 20000417 3 S16W52 0030 DAO 8966 20000418 7 S13W39 0020 BXO 8967 20000419 15 N23W30 0160 FAO beta-gamma 8968 20000419 5 S13W66 0060 CSO 8969 20000420 3 N11W20 0010 AXX 8970 20000420 42 S15E04 1090 EKC beta-gamma 8971 20000421 22 N18E02 0850 EKI 8972 20000421 5 N34W60 0230 EAO 8973 20000422 5 N22W64 0080 CAO 8974 20000423 S12W76 plage 8975 20000423 S25E11 plage Total number of sunspots: 107 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 2000.04 185.1 (1) 170.7 (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]