Solar Terrestrial Activity Report [Image] Last update April 22, 2000 at 03:50 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 active on April 21. Solar wind speed ranged between 477 and 554 km/sec under the influence of a coronal stream. Solar flare activity was low. Solar flux was 187.3, the planetary A index was 10 (3-hour K indices: 2214 3322, Boulder K indices: 2213 3321). Region 8955 was mostly quiet and stable, further C class flares are possible. Region 8958 decayed slowly and was quiet. Region 8959 was quiet and stable and has rotated off the visible disk. Region 8962 was quiet and stable. Region 8963 decayed slowly and will likely continue to produce C class flares. Region 8964 was quiet and stable, as were regions 8965 and 8966. Region 8967 could produce C and minor M class flares. Region 8968 developed further and could generate C flares and perhaps a minor M flare. Region 8969 was quiet and stable. Region 8970 is a large region with a huge leader spot, an isolated major flare is possible. New region 8971 rotated into view at the northeast limb and is likely capable of M class flaring. New region 8972 emerged in the northeast quadrant and has developed quickly, C flares are possible now and minor M flares could become possible if the current rate of development continues. Flares and CMEs A total of 11 C flares were recorded on April 21. Region 8963 produced a C2.3 flare at 00:59, a C1.7 flare at 09:28, a C1.2 flare at 15:08, a C1.4 flare at 15:23, a C1.8 flare at 19:25 and a C1.2 flare at 20:35 UTC. Region 8955 was the source of a C1.7 flare at 05:29 and a C1.8/1F flare at 22:35 UTC. Region 8967 generated a C1.9 flare at 21:47 UTC while region 8970 managed a C4.8 flare at 17:58 UTC. Numerous CMEs were observed during the day from a source behind the northwest limb. A moderately large 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 B9 level. Coronal holes No obvious coronal holes are approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to unsettled on April 22-23. 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 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 8953 20000409 S12W87 plage 8954 20000410 N32W79 plage 8955 20000410 11 S21W58 0120 EAO 8958 20000411 6 N18W66 0040 CSO 8959 20000412 3 S15W92 0030 BXO 8962 20000413 1 N23W27 0030 HSX 8963 20000413 8 N16W31 0040 CRO beta-gamma 8964 20000416 1 N35W44 0010 HRX 8965 20000417 3 S19E17 0010 BXO 8966 20000418 2 S13E25 0040 HSX 8967 20000419 9 N22E36 0160 EAO 8968 20000419 11 S12E01 0180 DAO 8969 20000420 2 N12E47 0020 HRX 8970 20000420 7 S15E68 0630 EKO beta-gamma 8971 20000421 3 N18E67 0400 EKO beta-gamma 8972 20000421 4 N32E03 0020 CSO Total number of sunspots: 71 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 2000.04 181.3 (1) 133.2 (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]