Solar Terrestrial Activity Report [Image] Last update April 23, 2002 at 03:30 UTC. Last minor update posted at 08:37 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 active on April 22. Solar wind speed ranged between 386 and 457 km/sec. The CME observed in connection with the X1 event in region 9906 on April 21 has not yet arrived. Should the CME fail to arrive by noon on April 23, there is a real possibility it will not arrive at all. Solar flare activity was low. Solar flux was 169.9, the planetary A index was 12 (3-hour K indices: 3423 3322, Boulder K indices: 3423 2332). Region 9909 was quiet and stable. Region 9910 decayed further and was quiet. Region 9912 decayed slowly and simplified. Region 9913 developed slowly early in the day, then decayed and became spotless by the end of the day. Region 9914 developed further, particularly in the trailing spots section and could soon become capable of minor M class flaring. Region 9915 developed at a moderate pace and has an increasing flare potential. At least C class flares are possible. Region 9916 was mostly unchanged and quiet. New region 9917 emerged in the southeast quadrant but decayed into spotless plage by the end of the day. New region 9918 emerged in the northeast quadrant near the central meridian, then decayed quickly and was spotless by late afternoon. New region 9919 rotated partly into view at the northeast limb. Comment added at 04:35 UTC on April 23: A strong solar wind shock was observed at ACE at 04:15 UTC. Minor to major geomagnetic storming is possible for the remainder of the day. Comment added at 08:37 UTC: The above solar wind shock was recorded at SOHO at 04:07 UTC with solar wind speed increasing abruptly from 420 to 610 km/sec. The interplanetary magnetic field was initially confused with several brief and strong southwards swings. A more sustained southward swing was observed between 06:30 and 07:20 UTC. The geomagnetic field is currently at major storm levels. Flares and CMEs A total of 7 C class events were recorded on April 22. Region 9906 produced a C7.7 flare from behind the southwest limb at 00:19 UTC. Region 9915 generated a C3.5 flare at 01:07 UTC. Region 9916 was the source of a C5.5 flare at 05:47 UTC. Region 9914 produced a C1.3 flare at 10:10 and a C1.4 flare at 14:41 UTC, while region 9912 managed a C2.8 flare at 12:10 UTC. The flare in region 9912 was associated with a weak type II radio sweep, no obvious CME was observed. April 21: Region 9906 produced a major long duration X1.6 proton event which began at 00:43 and peaked at 01:51 UTC. Strong type II and IV radio sweeps were recorded in association with this event. This event included a large filament eruption in the southwest quadrant as well. A very large, wide and extremely fast (exit speed estimated at above 2400 km/sec) CME was observed in LASCO C3 images. The CME became nearly a full halo CME with only a part of the southeast limb not covered. The outer edges of this monster solar storm could hit the Earth during the first half of April 23 and cause a geomagnetic storm. The background x-ray flux is at the class B8 level. Coronal holes A recurrent trans equatorial coronal hole will rotate into a geoeffective position on April 24-25. This coronal hole is not as large as it has been over the last rotations but could cause unsettled to active conditions on April 27-28. Forecast The geomagnetic field is expected to be quiet to major storm on April 23. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor to 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 the Earth within the next 5 days. 2) Material from a CME is likely to impact the 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 region numbered sunspots at Area Classification Comment midnight 9907 2002.04.11 S03W76 plage 9909 2002.04.14 1 N08W37 0050 HSX 9910 2002.04.15 6 S21W47 0080 CSO 9911 2002.04.18 S13W30 plage 9912 2002.04.18 15 N10W25 0320 DAI 9913 2002.04.19 1 S15W19 0020 HRX now spotless 9914 2002.04.19 9 N04E31 0150 DSO beta-gamma 9915 2002.04.21 9 N12E42 0120 DAO beta-gamma 9916 2002.04.21 8 S17E60 0150 DSO 9917 2002.04.22 2 S30E45 0020 CRO now spotless 9918 2002.04.22 3 N06E00 0010 BXO now spotless 9919 2002.04.22 1 N11E80 0060 HSX Total number of sunspots: 55 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) 2002.04 200.1 (1) 150.4 (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]