Solar Terrestrial Activity Report [Image] Last update April 23, 2000 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 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 22. Solar wind speed ranged between 390 and 516 km/sec. Solar flare activity was low. Solar flux was 201.8, the planetary A index was 7 (3-hour K indices: 2232 2222, Boulder K indices: 1123 1111). Region 8955 decayed slowly and was quiet, the region will rotate over the west limb on April 24. Region 8958 was quiet and stable and is rotating off the visible disk. Region 8962 was quiet and stable. Region 8963 decayed slowly and could produce further C class flares. Region 8964 decayed into spotless plage. Regions 8965 and 8966 were quiet and stable. Region 8967 developed slowly and could produce C and minor M class flares. Region 8968 was mostly unchanged and quiet, the region could generate C flares and perhaps a minor M flare. Region 8969 was quiet and stable. Region 8970 developed slowly and is a large region capable of producing a major flare. Region 8971 developed slowly and is a possible major flare producer. Region 8972 developed slowly and is probably capable of minor M class flaring. New region 8973 emerged in the northwest quadrant near region 8972. Flares and CMEs A total of 10 C flares were recorded on April 22. Region 8963 produced a C3.0 flare at 03:03 and a C3.6 flare at 06:01 UTC. Region 8971 was the source of a C2.0 flare at 15:59 UTC. Region 8970 generated a C2.6 flare at 18:09 and a C1.9 flare at 18:59 UTC. Region 8972 produced a C2.7 flare at 19:16, A C1.4 flare at 20:29, a C1.9 flare at 21:31 and a C3.3 flare at 21:54 UTC. An optically uncorrelated C7.1 flare was observed at 23:54 UTC. A prominence near the northeast limb erupted early on April 23 and produced a CME off the north pole and the northeast limb. 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 unsettled on April 23. On April 24 and 25 fairly weak CMEs could influence the geomagnetic field and cause unsettled and active intervals. 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 8955 20000410 7 S21W71 0060 ESO 8958 20000411 5 N18W81 0050 CSO 8962 20000413 1 N24W40 0020 HSX 8963 20000413 7 N17W44 0030 CSO beta-gamma 8964 20000416 N35W57 plage 8965 20000417 4 S16E00 0010 CRO 8966 20000418 4 S14E10 0010 CRO 8967 20000419 13 N22E23 0220 EAO 8968 20000419 9 S13W12 0190 DAO 8969 20000420 3 N11E34 0040 CSO 8970 20000420 15 S15E56 1010 EKI 8971 20000421 12 N17E54 0600 FKO beta-gamma 8972 20000421 13 N33W10 0110 DAO 8973 20000422 3 N20W12 0010 BXO Total number of sunspots: 96 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 2000.04 182.3 (1) 140.7 (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]