Solar Terrestrial Activity Report [Image] Last update April 19, 2000 at 04:45 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 18. Solar wind speed ranged between 387 and 538 km/sec, slowly increasing towards the end of the day. Solar flare activity was low. Solar flux was 160.4, the planetary A index was 7 (3-hour K indices: 2311 2331, Boulder K indices: 1311 1122). Region 8949 was quiet and stable rotated over the west limb. Regions 8951 and 8953 were quiet and stable. Region 8955 was mostly quiet and stable and has only a small chance of producing a minor M flare. Region 8958 decayed into spotless plage but has once again reemerged early on April 19 with a few spots. Region 8959 was quiet and stable. Region 8960 was quiet and is rotating off the visible disk. Region 8961 decayed into spotless plage. Region 8962 was quiet and stable. Region 8963 is developing at a moderate pace and is capable of producing an M flare. The region is a reversed polarity region and has fairly tight magnetic gradients. Region 8964 was quiet and stable, as was region 8965. New region 8966 rotated into view at the southeast limb. A fairly active region at the northeast limb has rotated partly into view and could be capable of at least C class flaring. Another region, further south, is about to rotate into view at the northeast limb. Flares and CMEs A total of 6 C flares were recorded on April 18. Region 8963 produced a C7.8 flare at 08:05 , a C4.2 flare at 14:15 and a C4.0 flare at 11:53 UTC. A moderately strong type II sweep accompanied the latter flare. Region 8963 is in a good position to produce geoeffective CMEs, and although there may have been a geoeffective CME associated with the type II sweep, no obvious halo CME was observed in LASCO images. A large filament eruption was observed starting at 23:36 UTC in the southern hemisphere. A wide and large partial halo coronal mass ejection was observed covering most of the southeast and southwest limbs as well as the south pole. The CME was probably not geoeffective, however, further studies of the event are required to increase the certainty of that assessment. The background x-ray flux is at the class B8 level. Coronal holes A well placed and fairly small coronal hole mainly in the northern hemisphere was in a geoeffective position on April 17-18. Forecast The geomagnetic field is expected to be quiet to active on April 19. A coronal stream will likely influence the geomagnetic field on April 20-21 causing unsettled to minor storm conditions. 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 8949 20000405 1 S17W91 0060 HSX 8951 20000407 2 N12W71 0070 CSO 8953 20000409 1 S13W47 0010 AXX 8954 20000410 N32W40 plage 8955 20000410 14 S22W19 0300 EAO 8956 20000410 N13W57 plage 8958 20000411 N18W25 plage 8959 20000412 5 S16W48 0010 CRO 8960 20000413 1 N20W86 0010 HRX 8961 20000413 S27W60 plage 8962 20000413 1 N23E11 0050 HSX 8963 20000413 12 N16E09 0080 DAI beta-gamma 8964 20000416 4 N34W04 0020 DSO 8965 20000417 4 S16E53 0010 BXO 8966 20000418 1 S13E65 0060 HSX Total number of sunspots: 46 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 2000.04 181.8 (1) 114.2 (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]