Solar Terrestrial Activity Report [Image] Last update April 22, 2001 at 04:45 UT. [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, 2001)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2001)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update April 2, 2001)] [Historical solar and geomagnetic data charts 1954-2000 (last update April 8, 2001)] Recent development The geomagnetic field was quiet to unsettled on April 21. Solar wind speed ranged between 347 and 405 km/sec. A weak solar wind shock was observed at SOHO at 14:57 UTC. Solar wind speed increased suddenly from 350 to 400 km/sec. The source of this disturbance is uncertain but may have been a CME from a filament eruption in the northwest quadrant a few days ago. Solar flare activity was low. Solar flux was 191.1, the planetary A index was 7 (3-hour K indices: 1212 2323, Boulder K indices: 2202 2424). Region 9429 was quiet and stable. Region 9431 developed further and was quiet. Region 9432 developed slowly and could produce C class flares. Region 9433 developed many new spots and has become more complex over the last day. There is a magnetic delta within the trailing penumbra. The region is capable of producing an X class flare. Region 9434 decayed further and has only one small spot left early on April 22. Region 9435 developed fairly quickly and could produce minor M class flares. New region 9436 rotated into view at the southeast limb. New region 9437 rotated into view at the northeast limb. Further regions will likely rotate into view at the northeast limb over the next couple of days. Flares and CMEs A total of 6 C class events were recorded on April 21. Region 9433 produced a C1.7 flare at 18:09, a C1.7 flare at 19:33, a C3.3 flare at 22:07 and a C3.6 flare at 22:46 UTC. The background x-ray flux is at the class B8 level. Coronal holes An isolated coronal hole in the northern hemisphere was in a possibly geoeffective position on April 19-20. Forecast The geomagnetic field is expected to be quiet to active on April 22, possibly with an isolated minor storm interval. A weak coronal stream based disturbance could start on April 22 and cause unsettled to active 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 Location region numbered no. at Area Classification Comment sunspots midnight 9429 2001.04.14 1 N08W31 0060 HSX 9431 2001.04.17 8 S11E00 0130 DAO 9432 2001.04.18 13 N08W16 0100 DAO 9433 2001.04.18 35 N16E40 0790 FKI beta-gamma-delta 9434 2001.04.19 2 N20W51 0020 CSO 9435 2001.04.19 15 S20E01 0210 DAO 9436 2001.04.21 1 S11E72 0070 HSX 9437 2001.04.21 1 N08E76 0050 HSX Total number of sunspots: 76 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 2000.01 158.1 90.1 112.9 (+1.8) 2000.02 174.1 112.9 116.8 (+3.9) 2000.03 208.2 138.5 119.9 (+3.1) 2000.04 184.2 125.5 120.8 (+0.9) cycle 23 sunspot max. 2000.05 184.9 121.6 119.0 (-1.8) 2000.06 179.8 124.9 118.7 (-0.3) 2000.07 202.3 170.1 119.8 (+1.1) 2000.08 163.0 130.5 118.6 (-1.2) 2000.09 182.1 109.7 116.2 (-2.4) 2000.10 167.4 100.1 (115.4 predicted, -0.8) 2000.11 178.8 106.5 (114.2 predicted, -1.2) 2000.12 173.6 104.5 (111.7 predicted, -2.5) 2001.01 166.6 95.7 (108.0 predicted, -3.7) 2001.02 146.6 80.1 (103.5 predicted, -4.5) 2001.03 177.7 114.2 (100.0 predicted, -3.5) 2001.04 171.4 (1) 112.0 (2) (98.8 predicted, -1.2) 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 25-40% 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 noted in solar links. Comments and suggestions are always welcome. ------------------------------------------------------------------------ Do you know about the survey which will be held this Summer among the listeners of WWV and WWVH? There is information about this survey at 16 minutes past the hour on WWV and at 47 minutes past the hour on WWVH. If you want to participate send an email with your name and address. ------------------------------------------------------------------------ [DX-Listeners' Club] [DX News] [StudyWeb]