Solar Terrestrial Activity Report [Image] Last update April 25, 2000 at 02:20 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update 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 minor storm on April 24. Solar wind speed ranged between 398 and 577 km/sec. A solar wind shock was observed at 03:55 at ACE with a sudden increase in solar wind speed from 400 to 500 km/sec. The interplanetary magnetic field swung moderately southwards and caused the geomagnetic field to become unsettled to active. The source of the disturbance was likely the halo CME observed on April 20. What appears to have been a second shock was observed at 09:00 UTC at ACE with a solar wind increase from 480 to 530 km/sec. The IMF total field strengthened and the southward swing (which had been slowly decreasing) increased to moderate to strong levels for a few hours. Solar flare activity was low. Solar flux was 205.6, the planetary A index was 21 (3-hour K indices: 2344 5333, Boulder K indices: 2443 4312). Regions 8962 and 8963 were quiet and stable, both regions could become spotless today. Region 8965 decayed slowly and was quiet. Region 8966 was quiet and stable. Regions 8967 and 8968 were mostly quiet and stable. Region 8969 was quiet and stable. Region 8970 did not change significantly and remains the most likely site of a major flare. Region 8971 simplified but could still produce a major flare. Region 8972 developed slowly and could produce M class flares. Region 8973 developed slowly and could produce a minor M flare. Region 8974 was quiet and stable. Region 8975 decayed into spotless plage. Flares and CMEs A total of 9 C flares were recorded on April 24. Region 8967 produced a C2.7 flare at 01:11 UTC. Region 8972 was the source of a C1.6 flare at 03:36, a C1.9 flare at 17:46 and a C2.9 flare at 18:03 UTC. Region 8963 generated a C1.1 flare at 13:06 UTC while region 8964 managed a C1.0 flare at 16:28 UTC. The background x-ray flux is at the class B6 level. Coronal holes No obvious coronal holes are approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to active on April 24-25. 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 8962 20000413 1 N24W65 0010 AXX 8963 20000413 2 N17W70 0000 BXO 8964 20000416 N35W83 plage 8965 20000417 6 S16W27 0040 DSO 8966 20000418 3 S12W15 0000 BXO 8967 20000419 11 N22W04 0180 EAO 8968 20000419 9 S13W39 0130 DSO 8969 20000420 1 N12E07 0020 HSX 8970 20000420 27 S15E30 1060 EKC beta-gamma-delta 8971 20000421 15 N18E28 0910 EKO 8972 20000421 16 N34W34 0220 EHI beta-gamma 8973 20000422 10 N21W39 0110 DSO 8974 20000423 1 S21W50 0000 AXX 8975 20000423 S25E37 plage Total number of sunspots: 102 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 2000.04 184.2 (1) 156.5 (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]