Solar Terrestrial Activity Report [Image] Last update April 24, 2000 at 02:55 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 23. Solar wind speed ranged between 379 and 478 km/sec. Solar flare activity was low. Solar flux was 206.1, the planetary A index was 8 (3-hour K indices: 1133 2322, Boulder K indices: 2122 2312). Region 8955 decayed slowly and was quiet, the region is rotating off the visible disk. Regions 8962 and 8963 were quiet and stable. Region 8965 developed slowly and may be capable of C class flaring. Region 8966 was quiet and stable. Regions 8967 and 8968 were mostly unchanged and could produce C and minor M class flares. Region 8969 was quiet and stable. Region 8970 developed further and has a weak magnetic delta configuration, the region could produce a major flare any time over the next few days. Region 8971 developed further and has a magnetic delta configuration as well. Major flares, even X class flares, are possible. Region 8972 developed slowly and could produce M class flares. Region 8973 is developing at a moderate pace and is likely to produce C flares, a minor M flare is becoming a possibility. New region 8974 emerged in the southwest quadrant. New region 8975 emerged in the southeast quadrant. Flares and CMEs A total of 4 C flares were recorded on April 23. Region 8967 produced a C2.1 flare at 06:24 UTC. Region 8970 generated a C2.7 flare at 13:49 UTC. An optically uncorrelated C4.7 flare occurred at 01:25 UTC. A bright surge on the northwest limb was observed at 12:23 UTC. This may have been related to a large flare behind the northwest limb and an associated very large coronal mass ejection off the west limb, the north and south poles as well as the northeast limb. Additionally background proton flux values increased slightly after 16h UTC indicating that the flare was a proton flare. April 21: A moderately large multiple filament eruption was observed in the southwest quadrant near the central meridian and the equator starting at 21:12 UTC in LASCO EIT images. This event may have produced a geoeffective CME, a CME which could impact Earth on April 25. April 20: A weak halo coronal mass ejection was observed starting at 20:42 in LASCO C3 images. This may have been related to the C4.7 flare at 19:35 UTC in region 8963, however, there is a possibility the CME could have had a backside origin. If region 8963 was the CME source a weak terrestrial impact will be possible from late on April 23 until late on April 24. The background x-ray flux is at the class B8 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 8955 20000410 2 S20W84 0030 CSO 8962 20000413 1 N24W53 0020 HSX 8963 20000413 2 N17W57 0020 BXO 8964 20000416 N35W70 plage 8965 20000417 9 S16W13 0080 DAO 8966 20000418 3 S13W01 0000 BXO 8967 20000419 13 N22E09 0180 EAO 8968 20000419 8 S13W26 0170 DAO 8969 20000420 2 N12E20 0020 HSX 8970 20000420 31 S15E43 1210 EKC beta-gamma-delta 8971 20000421 16 N18E41 0860 FKO beta-gamma-delta 8972 20000421 16 N34W21 0200 DAO beta-gamma 8973 20000422 7 N20W26 0070 DAO 8974 20000423 1 S21W36 0000 AXX 8975 20000423 1 S25E50 0000 AXX Total number of sunspots: 112 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 2000.04 183.3 (1) 149.1 (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]