Solar Terrestrial Activity Report [Image] Last update April 18, 2002 at 04:50 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, 2002)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2002)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update April, 2002)] [Historical solar and geomagnetic data charts 1954-2002 (last update April 13, 2002)] Recent development The geomagnetic field was quiet to major storm on April 17. Solar wind speed ranged between 319 and 593 km/sec. A strong solar wind shock was observed at 10:13 UTC at SOHO with a sudden increase in solar wind speed from 350 to 500 km/sec. The interplanetary magnetic field was at times strongly to very strongly southwards after the shock. After 01h UTC on April 18 the IMF has been constantly strongly southwards. Solar flare activity was moderate. Solar flux was 193.5, the planetary A index was 41 (3-hour K indices: 2326 6653, Boulder K indices: 2335 5643). Region 9896 was quiet and stable and rotated quietly over the southwest limb early today. Region 9899 was quiet and stable and will rotate over the northwest limb on April 19. Region 9902 decayed slowly and quietly. Region 9906 decayed slightly after the long duration M class event. There is still a magnetic delta structure in the trailing spots section. A major flare is possible. Region 9907 decayed further and was quiet. No significant flares are expected from this region. Region 9909 was quiet and stable. Region 9910 developed slowly and could produce C class flares. Flares and CMEs A total of 7 C and 1 M class events were recorded on April 17. Region 9905 at the southwest limb produced a C9.9 flare at 00:40, a C2.3 flare at 02:37, a C1.8 flare at 06:55, a C6.9 flare at 13:42 and a C9.8 flare at 16:58 UTC. Region 9910 was the source of a C4.4 flare at 23:19 UTC. Region 9906 generated a long duration M2.6/2N event peaking at 08:24 UTC. A full halo CME was observed in LASCO images. The CME will likely reach the Earth on April 19 and cause active to severe geomagnetic storm conditions. The background x-ray flux is at the class C1 level. Coronal holes A well placed small coronal hole in the southern hemisphere near the equator will rotate into a geoeffective position on April 18-19. Forecast The geomagnetic field is expected to be unsettled to severe storm on April 18-19. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is useless. 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 Location region numbered no. at Area Classification Comment sunspots midnight 9896 2002.04.05 1 S10W85 0040 HSX 9898 2002.04.06 S18W80 plage 9899 2002.04.06 1 N17W71 0100 HSX 9902 2002.04.07 3 N12W55 0050 CSO 9903 2002.04.08 N17W38 plage 9906 2002.04.11 26 S14W41 0650 EKI beta-gamma-delta 9907 2002.04.11 25 S03W07 0100 EAI 9909 2002.04.14 3 N08E28 0100 CSO 9910 2002.04.15 8 S20E22 0060 DAO Total number of sunspots: 67 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 2000.04 184.2 125.5 120.8 cycle 23 sunspot max. 2000.07 202.3 170.1 119.8 2001.02 146.6 80.6 104.0 (-4.7) 2001.03 177.7 113.5 104.8 (+0.8) 2001.04 177.7 107.7 107.5 (+2.7) 2001.05 147.1 96.6 108.6 (+1.1) 2001.06 173.0 134.0 109.8 (+1.2) 2001.07 131.3 82.2 111.7 (+1.9) 2001.08 162.9 106.8 113.6 (+1.8) 2001.09 233.2 150.7 114.1 (+0.5) 2001.10 207.6 125.5 (113.3 predicted, -0.8) 2001.11 210.6 106.5 (112.7 predicted, -0.6) 2001.12 235.1 132.2 (109.3 predicted, -3.4) 2002.01 226.6 113.9 (106.0 predicted, -3.3) 2002.02 205.0 108.0 (104.6 predicted, -1.4) 2002.03 179.5 98.1 (100.4 predicted, -4.2) 2002.04 206.7 (1) 122.3 (2) (94.5 predicted, -5.9) 1) Running average based on the daily 20:00 UT solar flux value at 2800 MHz. 2) Unofficial, accumulated value based on the Boulder (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% 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 noted in solar links. Comments and suggestions are always welcome. ------------------------------------------------------------------------ [DX-Listeners' Club] [DX News]