Solar Terrestrial Activity Report [Image] Last update April 28, 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 27. Solar wind speed ranged between 402 and 480 km/sec under the influence of a weak coronal stream. A very strong solar wind shock was observed at 04:30 UT on April 28. Solar wind speed increased abruptly by an incredible 360 km/sec going from 470 to 830 km/sec. There was a substantial increase in proton densities at the time of the shock. Earth should receive an impact at about 05 UT. Very severe storming is possible today. Solar flare activity was moderate. Solar flux was 190.8, the planetary A index was 6 (3-hour K indices: 2102 3321, Boulder K indices: 2211 1210). Region 9431 decayed and was spotless by early evening. Region 9433 decayed slowly but still has a magnetic delta within the large trailing penumbra. There is still a chance of a major flare, however, C and minor M class flares are more likely. Region 9435 was quiet and stable (and will rotate off the visible disk today), as were regions 9436 and 9437. Region 9439 decayed and could become spotless today. Region 9440 was quiet and stable. Region 9441 developed at a moderate pace and could produce C flares. Region 9442 was quiet and stable. New region 9443 emerged in the southeast quadrant, the region appears to be spotless early on April 28. Flares and CMEs A total of 5 C and 1 M class events were recorded on April 27. Region 9433 produced a C3.4 flare at 01:08 and a C3.7 flare at 02:00 UT. April 26: Region 9433 was the source of a major impulsive M7.8/2B flare at 13:12 UT. This flare was superimposed on a long duration M1.8 event which involved filament eruptions within and near region 9433. A large full halo coronal mass ejection was observed in LASCO C3 images. The background x-ray flux is at the class B8 level. Coronal holes An isolated coronal hole in the northern hemisphere could rotate into a geoeffective position on April 29 but may be located too far to the north to have any effect on the geomagnetic field. Forecast The geomagnetic field is expected to be quiet to very severe storm on April 28 and unsettled to major storm on April 29. 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 9431 2001.04.17 1 S10W85 0000 AXX 9433 2001.04.18 45 N17W38 0910 FKI beta-gamma-delta 9435 2001.04.19 3 S20W80 0160 CAO 9436 2001.04.21 1 S10W06 0160 HSX 9437 2001.04.21 5 N09W05 0030 CAO 9438 2001.04.24 S13W17 plage 9439 2001.04.25 1 S20W55 0020 HRX 9440 2001.04.26 6 N08E05 0030 DRO 9441 2001.04.26 15 N08E38 0150 DAO 9442 2001.04.26 1 N28E47 0060 HSX 9443 2001.04.27 3 S10E21 0010 BXO Total number of sunspots: 81 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) 2001.04 176.4 (1) 146.5 (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]