Solar Terrestrial Activity Report [Image] Last update April 30, 2001 at 03:40 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 29. Solar wind speed ranged between 468 and 803 km/sec. Solar flare activity was low. Solar flux was 191.7, the planetary A index was 15 (3-hour K indices: 4422 3221, Boulder K indices: 4432 3221). Region 9433 decayed further. The large trailing penumbra appears to be splitting into two separate penumbras. A completion of the split process would remove the only magnetic delta configuration remaining within the region. M class flares are possible until the region rotates out of view on May 2. Region 9436 was quiet and stable. Region 9437 decayed slowly and could become spotless today or tomorrow. Region 9441 developed slowly and was quiet. The region is becoming more complex and could soon start producing minor M class flares. Region 9442 was quiet and stable. Region 9444 was quiet and stable. Region 9445 developed slowly and could produce minor M class flares. New region 9446 emerged in the southwest quadrant. Another new region emerged to the northeast of region 9441 and should be numbered today. Flares and CMEs A total of 9 C class events were recorded on April 29. Region 9433 produced a C1.8 flare at 03:54 UT. Region 9445 generated a C1.4 flare at 17:27, a C2.4 flare at 17:46 and a C2.7 flare at 19:24 UT. April 28: A filament eruption was observed in the southern hemisphere near the center of the solar disk beginning at 01:48 UT in LASCO EIT images. Although no obvious CME was observed in LASCO C3 images, the eruption may have set off a small geoeffective CME. The CME could reach Earth early on May 1. The background x-ray flux is at the class B9 level. Coronal holes An isolated coronal hole in the northern hemisphere was likely in a geoeffective position on April 29. A coronal hole in the southern hemisphere will rotate into a geoeffective position on May 2. Forecast The geomagnetic field is expected to be quiet to unsettled on April 30 and quiet to active on May 1-2. 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 9433 2001.04.18 30 N18W63 0780 FKI beta-gamma-delta 9436 2001.04.21 1 S09W33 0110 HSX 9437 2001.04.21 2 N10W32 0010 AXX 9438 2001.04.24 S13W43 plage 9439 2001.04.25 S23W81 plage 9440 2001.04.26 N08W21 plage 9441 2001.04.26 28 N07E11 0190 DAI 9442 2001.04.26 1 N28E22 0060 HSX 9443 2001.04.27 S10W05 plage 9444 2001.04.28 6 S11E52 0050 CSO 9445 2001.04.28 10 N24E61 0190 DAO beta-gamma 9446 2001.04.29 3 S05W22 0010 CRO 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) 2001.04 177.3 (1) 157.7 (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]