Solar Terrestrial Activity Report [Image] Last update April 19, 2002 at 03:25 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 unsettled to severe storm on April 18. Solar wind speed ranged between 466 and 574 km/sec. The interplanetary magnetic field was strongly southwards for most of the first half of the day, then slowly swung northwards towards the end of the day. Solar flare activity was low. Solar flux was 188.2, the planetary A index was 54 (3-hour K indices: 6765 4443, Boulder K indices: 5755 4422). Region 9899 rotated quietly over the northwest limb. Region 9902 decayed further and will rotate over the northwest limb on April 20. Region 9906 decayed further in the trailing spot section and lost its magnetic delta structure. Some new development was observed in the leading spots as positive polarity magnetic flux emerged at the southern edge of the large leading magnetically negative penumbra. A major flare is still possible. Region 9907 decayed further and was mostly quiet. Region 9909 was quiet and stable. Region 9910 developed slowly early in the day, then stabilized. The region is magnetically simple and is currently unlikely to produce significant flares. New region 9911 emerged in the southeast quadrant and is unimpressive. New region 9912 emerged in the northeast quadrant and may be capable of further development. Flares and CMEs A total of 6 C class events were recorded on April 18. Region 9905, behind the southwest limb, produced a C4.0 flare at 03:46 and a C3.0 long duration event peaking at 16:12 UTC. Region 9893, behind the northwest limb, was the apparent source of a long duration C9.4 event peaking at 07:02 UTC. Region 9907 generated a C1.5 flare at 14:33 UTC. April 17: Region 9906 produced 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 B8 level. Coronal holes A well placed small coronal hole in the southern hemisphere near the equator was in a geoeffective position on April 18-19. Forecast The geomagnetic field is expected to be unsettled to severe storm on April 19, quiet to minor storm on April 20 and quiet to active on April 21. 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 9899 2002.04.06 1 N19W86 0100 HSX 9902 2002.04.07 1 N12W70 0060 HSX area too large 9903 2002.04.08 N17W51 plage 9906 2002.04.11 33 S14W55 0770 EKC beta-gamma 9907 2002.04.11 16 S02W22 0070 DAO 9909 2002.04.14 3 N08E15 0100 CSO 9910 2002.04.15 18 S20E07 0210 DAO 9911 2002.04.18 4 S13E23 0020 BXO 9912 2002.04.18 4 N11E28 0050 DSO Total number of sunspots: 80 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) 2002.04 205.7 (1) 127.7 (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]