Solar Terrestrial Activity Report [Image] Last update April 23, 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 unsettled to minor storm on April 22. Solar wind speed ranged between 310 and 391 km/sec. Solar flare activity was moderate. Solar flux was 192.5, the planetary A index was 28 (3-hour K indices: 4354 5534, Boulder K indices: 4344 5423). Region 9429 was quiet and stable. Region 9431 decayed slowly and was quiet. Region 9432 was mostly unchanged and quiet. Region 9433 developed slowly and has major flare potential. An X class proton flare is possible. Region 9434 decayed and was spotless by early evening. Region 9435 did not change significantly and was mostly quiet. Regions 9436 and 9437 were quiet and stable. Flares and CMEs A total of 13 C and 1 M class events were recorded on April 22. Region 9433 produced a C1,8 flare at 01:33, a C1.7 flare at 01:48, a C2.8 flare at 05:20, a C3.7 flare at 08:13, a C2.2 flare at 17:07, an impulsive M3.2/1N flare at 20:44 UT, a C1.7 flare at 21:37, a C3.5 flare at 22:05 and finally a C3.8 flare at 22:41 UT. A strong type II sweep was associated with the M3 flare. There was no well defined CME in LASCO C3 images, however, a diffuse CME could be observed and is likely to cause an increase in geomagnetic activity on April 24 or 25. The M3 flare apparently triggered a filament eruption in the northern hemisphere stretching from just west of the region and into the northwest quadrant. The background x-ray flux is at the class B8 level. Coronal holes A coronal hole in the southern hemisphere could rotate into a geoeffective position on April 23 and cause unsettled to active conditions on April 26. Forecast The geomagnetic field is expected to be quiet to active on April 23 and most of April 24. A CME could arrive late on April 24 or on April 25 and cause unsettled to major storm 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 N08W45 0050 HSX 9431 2001.04.17 7 S11W15 0060 DAO 9432 2001.04.18 12 N08W34 0090 DAO 9433 2001.04.18 47 N17E26 0760 FKI beta-gamma-delta 9434 2001.04.19 1 N17W67 0010 AXX now spotless 9435 2001.04.19 14 S20W12 0250 DAO 9436 2001.04.21 1 S10E59 0100 HSX 9437 2001.04.21 1 N10E61 0060 HAX Total number of sunspots: 84 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) 2001.04 172.3 (1) 117.5 (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]