Solar Terrestrial Activity Report [Image] Last update April 18, 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 mostly quiet to unsettled with a single minor storm interval 06-09h UTC on April 17. Solar wind speed ranged between 416 and 495 km/sec. Solar flare activity was low. Solar flux was 157.9, the planetary A index was 14 (3-hour K indices: 3353 1222, Boulder K indices: 2343 2322). Region 8949 was quiet and stable and will be rotating off the visible disk late today. Regions 8951 and 8953 were quiet and stable. Region 8955 has minor M class flare potential and was mostly unchanged compared to the preceding day. Region 8956 decayed into spotless plage. Region 8958 reemerged with a single spot but is spotless again early on April 18. Regions 8959, 8960, 8962 and 8963 were mostly quiet and stable. Region 8961 reemerged with a couple of spots, the region is spotless early on April 18. Region 8964 was quiet and stable. New region 8965 rotated into view at the southeast limb. Another region at the southeast limb is rotating into view. Flares and CMEs A total of 4 C flares were recorded on April 17. Region 8955 produced a C2.5/1F flare at 00:28 and a C3.7/1N flare at 17:34 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. A small coronal hole to the south of region 8955 was probably too far to the south to be geoeffective when it rotated over the central meridian on April 17-18. Forecast The geomagnetic field is expected to be quiet to unsettled on April 18-19. A coronal stream will likely influence the geomagnetic field on April 21 and 22 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 2 S20W79 0080 HAX 8951 20000407 4 N12W57 0080 CSO 8952 20000407 S23W82 plage 8953 20000409 1 S13W34 0010 HRX 8954 20000410 N32W27 plage 8955 20000410 13 S22W06 0320 EAO beta-gamma 8956 20000410 N13W44 plage 8958 20000411 1 N18W12 0000 AXX 8959 20000412 6 S17W34 0020 CRO 8960 20000413 1 N19W74 0020 HRX 8961 20000413 2 S27W47 0010 AXX 8962 20000413 1 N24E24 0060 HAX 8963 20000413 7 N16E22 0040 CRO 8964 20000416 6 N34E08 0030 CAO 8965 20000417 2 S16E66 0010 BXO 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 2000.04 183.0 (1) 109.0 (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]