Solar Terrestrial Activity Report [Image] Last update April 21, 2002 at 04:20 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 at major to severe storm levels during the first half of April 20 and quiet to active during the latter half of the day. Solar wind speed ranged between 465 and 650 km/sec. Solar flare activity was low. Solar flux was 177.3, the planetary A index was 62 (3-hour K indices: 7776 4442, Boulder K indices: 6645 4443). Region 9906 was mostly unchanged as it began to rotate out of view at the southwest limb. Another major flare is possible while the region is near the limb. Region 9907 decayed further and could become spotless today. Region 9909 decayed slowly and quietly. Region 9910 decayed further and could loose most of the remaining trailing spots today. Region 9911 decayed and was spotless by the end of the day. Region 9912 developed slowly and could produce minor M class flares. Region 9913 decayed and could become spotless today. Region 9914 developed slowly and quietly. SEC/NOAA failed to number a new small region near the northeast limb. Another spotted region at the southeast limb is rotating into view early on April 21. Flares and CMEs A total of 10 C class events were recorded on April 20. Region 9912 produced a C4.1 flare at 15:48 UTC. None of the other C flares were optically correlated. Region 9906 finally produced a major flare early on April 21. A long duration X1.6 proton event began at 00:43 and peaked at 01:51 UTC. Soon after a quick increase in energetic protons was noted at the Earth and a significant proton event is currently in progress. The above 10 MeV proton flux is quickly approaching 1000 pfu whilst the above 100 MeV proton flux appears to have peaked at 18 pfu. A polar cap absorption event is in progress and is likely to make radio propagation over high latitude paths nearly impossible over the next few days. No new LASCO images have become available online since 19h UTC on April 20 and it is therefore difficult to determine if the CME associated with the X1 event will be geoeffective or not. Even if the flare occurred near the southwest limb there is a chance of a sideways CME impact late on April 22 or sometime on April 23. 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 was in a geoeffective position on April 18-19. A large recurrent trans equatorial coronal hole will rotate into a geoeffective position on April 24-26. Forecast The geomagnetic field is expected to be quiet to active on April 21-22. There is a possibility of a minor CME impact from late on April 22 and this could cause unsettled to minor storm conditions on April 23. 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 9903 2002.04.08 N17W77 plage 9906 2002.04.11 27 S14W79 0680 EAC beta-gamma 9907 2002.04.11 5 S03W48 0070 DAO area too large 9909 2002.04.14 6 N07W10 0100 CAO 9910 2002.04.15 23 S20W06 0180 EAO too many spots 9911 2002.04.18 8 S13W04 0030 DSO now spotless 9912 2002.04.18 26 N10E02 0200 DAO beta-gamma 9913 2002.04.19 6 S16E10 0030 CSO 9914 2002.04.19 4 N05E59 0040 CAO Total number of sunspots: 105 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) 2002.04 203.0 (1) 139.9 (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]