Solar Terrestrial Activity Report [Image] Last update April 27, 2001 at 03:50 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 26. Solar wind speed ranged between 390 and 468 km/sec under the influence of a weak coronal stream. Solar flare activity was high. Solar flux was 196.2, the planetary A index was 7 (3-hour K indices: 1232 2321, Boulder K indices: 1332 3322). Region 9431 decayed and could become spotless today. Region 9432 has rotated off the visible disk. Region 9433 decayed slowly losing several spots and some of its areal coverage. The magnetic delta within the large trailing penumbra intensified and could cause further major flares. Region 9435 was quiet and stable, as was region 9436. Region 9437 was mostly quiet and stable. Region 9439 was quiet and stable. New region 9440 emerged in the northeast quadrant. New region 9441 emerged in the northeast quadrant near the northeast limb. New region 9442 rotated into view at the northeast limb. Flares and CMEs A total of 3 C and 2 M class events were recorded on April 26. Region 9433 produced a C3.4 flare at 01:08 and a C3.7 flare at 02:00 UT. The region 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 CME will impact Earth sometime between noon on April 28 and noon on April 29 and could cause minor to very severe geomagnetic storming. The background x-ray flux is at the class C1 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 unsettled on April 27 and at least the first half of April 28. A CME will impact the magnetosphere either during the latter half of April 28 or the first half of April 29 and could cause minor to very severe storming. 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 S11W71 0010 AXX 9432 2001.04.18 1 N08W86 0030 HRX 9433 2001.04.18 64 N17W25 0890 FKI beta-gamma-delta 9435 2001.04.19 4 S21W65 0180 DAO 9436 2001.04.21 1 S10E07 0160 HSX 9437 2001.04.21 9 N09E07 0040 CSO 9438 2001.04.24 S13W04 plage 9439 2001.04.25 2 S21W45 0020 CSO 9440 2001.04.26 6 N07E18 0010 BXO 9441 2001.04.26 4 N08E51 0030 CSO 9442 2001.04.26 1 N28E59 0040 HSX Total number of sunspots: 93 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) 2001.04 175.8 (1) 140.5 (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]