Solar Terrestrial Activity Report [Image] Last update April 16, 2000 at 04:40 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 to unsettled on April 15. Solar wind speed ranged between 277 and 360 km/sec. A disturbance arrived at ACE at about 16h UTC and intensified slowly until it peaked near 04h UTC on April 16. The source of the disturbance may have been the weak coronal stream which was forecasted to arrive on April 15. Solar flare activity was moderate. Solar flux was 163.7, the planetary A index was 7 (3-hour K indices: 1122 2233, Boulder K indices: 1121 2213). Region 8948 was mostly quiet and is rotating over the west limb. Region 8949 was quiet and stable, as were regions 8951, 8953 and 8954. Region 8955 quickly developed strong magnetic gradients near the large trailing spot and this was where all the flares had their origin. The region will likely produce further M flares and there is a chance of a major flare as well. Regions 8956, 8959, 8960, 8962 and 8963 were quiet and stable. Region 8958 decayed into spotless plage. Flares and CMEs A total of 8 C flares and 2 M flares were recorded on April 15. Region 8948 produced a C1.7 flare at 15:37 UTC. Region 8955 generated a C3.4 flare at 00:07, an impulsive M4.3 flare at 10:18, a C3.0 flare at 13:43, an M2.2/1N flare at 14:48, a C7.7/1N flare at 19:05 and a C6.5 flare at 21:43 UTC. The background x-ray flux is at the class B5 level. Coronal holes A well placed and fairly small coronal hole mainly in the northern hemisphere will rotate into a geoeffective position on April 18-19. A small coronal hole to the south of region 8955 is probably too far to the south to be geoeffective when it rotates over the central meridian on April 17-18. Forecast The geomagnetic field is expected to be quiet to active on April 16, with a slight chance of a minor storm interval early in the day. Quiet to unsettled is likely on April 17. 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 8948 20000404 3 S16W76 0060 DSO 8949 20000405 2 S19W52 0050 HAX 8951 20000407 6 N12W31 0100 DSO 8952 20000407 S23W56 plage 8953 20000409 4 S16W06 0020 CRO 8954 20000410 1 N32W01 0000 AXX 8955 20000410 19 S22E20 0350 EAO beta-gamma 8956 20000410 8 N12W16 0020 CRO 8957 20000410 S12W79 plage 8958 20000411 N17E17 plage 8959 20000412 9 S17W13 0060 CAO 8960 20000413 12 N19W43 0040 CSO 8961 20000413 S25W19 plage 8962 20000413 1 N22E49 0060 HSX 8963 20000413 2 N16E49 0010 AXX Total number of sunspots: 67 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 2000.04 186.3 (1) 97.8 (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]