Solar Terrestrial Activity Report [Image] Last update April 8, 2001 at 05:00 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 active on April 7. Solar wind speed ranged between 438 and 581 km/sec. A solar wind shock was observed at 16:59 UT at ACE. Solar wind speed jumped from 450 to 550 km/sec. After an initial couple of moderate southerly excursions in the interplanetary magnetic field, the IMF was northwards for the remainder of the day. The source of the disturbance is highly likely the halo CME observed on April 5. Solar flare activity was low. Solar flux was 179.5, the planetary A index was 16 (3-hour K indices: 3432 2443, Boulder K indices: 4432 3453). Regions 940> ------------------------------------------------------------------------ Transfer interrupted! ion 9412 decayed into spotless plage. Region 9413 rotated off the visible disk. Region 9415 was mostly unchanged, the magnetic delta weakened. The region is still capable of producing occasional major flares. Region 9417 developed slowly and could produce a minor M class flare. Region 9418 was mostly unchanged and could produce minor M class flares. Region 9419 reemerged with a couple of spots, the region is spotless again early on April 8. Region 9420 was quiet and stable. New region 9421 emerged in the southwest quadrant. New region 9422 rotated into view at the southeast limb. Flares and CMEs Only 1 C class event was recorded on April 7, an optically uncorrelated C2.3 flare at 10:39 UT. A full halo CME was observed in LASCO C3 images starting at 18:20 UT. The major part of the CME was directed westwards. No filament eruption was observed in LASCO EIT images and the source of the CME was likely on the backside of the sun. April 6: Region 9415 produced an impressive major X5.6 flare at 19:21 UT. A large and fast full halo coronal mass ejection was observed in LASCO C2 and C3 images after the eruption. The CME is geoeffective and could trigger a major geomagnetic storm on April 8. The background x-ray flux is at the class B6 level. Coronal holes No obvious coronal holes are currently approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to severe storm on April 8. 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 9404 2001.03.27 S03W85 plage 9406 2001.03.28 1 N27W60 0150 HSX 9407 2001.03.28 1 N11W68 0100 HSX 9410 2001.03.30 S36W60 plage 9411 2001.03.30 N08W57 plage 9412 2001.03.30 S16W26 plage 9414 2001.04.02 S23W06 plage 9415 2001.04.03 23 S21E21 0880 EKO beta-gamma-delta 9416 2001.04.03 N17W72 plage 9417 2001.04.03 20 S08E01 0160 DAO 9418 2001.04.04 11 N26E32 0210 EAO 9419 2001.04.04 2 N08W51 0010 AXX 9420 2001.04.05 2 S07E49 0070 HSX 9421 2001.04.06 2 S15W42 0010 CSO 9422 2001.04.06 1 S13E78 0050 HAX Total number of sunspots: 63 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 (114.6 predicted, -1.6) 2000.11 178.8 106.5 (112.6 predicted, -2.0) 2000.12 173.6 104.5 (110.1 predicted, -2.5) 2001.01 166.6 95.7 (106.3 predicted, -3.8) 2001.02 146.6 80.1 (101.9 predicted, -4.4) 2001.03 177.7 114.2 (98.4 predicted, -3.5) 2001.04 213.2 (1) 48.1 (2) (97.1 predicted, -1.3) 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]