Solar Terrestrial Activity Report [Image] Last update April 21, 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 active on April 20. Solar wind speed ranged between 429 and 569 km/sec under the influence of a coronal stream. Solar flare activity was low. Solar flux was 180.6, the planetary A index was 14 (3-hour K indices: 3342 3332, Boulder K indices: 3433 4332). Region 8953 decayed into spotless plage. Region 8955 was mostly quiet and stable, further C class flares are possible. Region 8958 developed further and could produce C flares. Region 8959 was mostly quiet and stable. Region 8962 was quiet and stable. Region 8963 decayed slowly but could produce further C class flares. Region 8964 was mostly 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. New region 8969 rotated into view at the northeast limb. New region 8970 rotated partly into view at the southeast limb. The region has a large leader spot and may be capable of M class flaring. Flares and CMEs A total of 7 C flares were recorded on April 20. Region 8963 produced a C1.6 flare at 01:00 and a C4.7 flare at 19:35 UTC. Region 8967 was the source of a C1.8 flare at 07:23 UTC. Region 8969 generated the largest flare of the day, a C8.6 event at 10:33 UTC. Region 8966 produced a C1.3 flare at 21:03 UTC while region 8955 managed a C1.3 flare at 21:44 UTC. A strong type II sweep was observed between 21:13 and 21:20 UTC, its origin is not yet certain. A weak halo coronal mass ejection was observed starting at 20:42 in LASCO C3 images. This may have been related to the C4 flare in region 8963 and will be investigated further to determine if it could be geoeffective. 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 21 and quiet to unsettled on April 22. 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 S12W74 plage 8954 20000410 N32W66 plage 8955 20000410 10 S21W46 0170 EAO 8956 20000410 N13W83 plage 8958 20000411 8 N19W53 0060 DSO 8959 20000412 2 S16W78 0010 AXX 8961 20000413 S27W86 plage 8962 20000413 1 N23W15 0030 HSX 8963 20000413 11 N16W18 0060 CAO 8964 20000416 2 N34W31 0010 HRX 8965 20000417 3 S17E26 0010 BXO 8966 20000418 2 S13E38 0040 HSX 8967 20000419 6 N21E49 0200 EAO 8968 20000419 11 S13E14 0090 DAO 8969 20000420 1 N13E62 0080 HRX 8970 20000420 2 S14E77 0350 HKX Total number of sunspots: 59 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 2000.04 181.0 (1) 126.1 (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]