Solar Terrestrial Activity Report [Image] Last update April 25, 2001 at 04:20 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 24. Solar wind speed ranged between 334 and 465 km/sec under the influence of a weak coronal stream (which began late on April 23). Solar flare activity was moderate. Solar flux was 193.5, the planetary A index was 8 (3-hour K indices: 1232 2322, Boulder K indices: 1232 2322). Region 9429 decayed slowly and was quiet, the region will rotate off the visible disk on April 26. Region 9431 decayed slowly and quietly. Region 9432 decayed slowly and was quiet. Region 9433 developed further with many new spots emerging. There are currently three magnetic deltas, the strongest is near the large trailing penumbra with the weaker ones located near the center and near the leading spots. The region has a high potential for producing a major X class flare. Region 9435 decayed slowly and was quiet. Regions 9436 and 9437 were quiet and stable. New region 9438 emerged in the southeast quadrant, the region appears to be spotless early on April 25. Flares and CMEs A total of 5 C and 5 M class events were recorded on April 24. Region 9433 produced a C5.3 flare at 00:22, a C3.4 flare at 03:57, an M2.1/1N flare at 05:42, an M3.1/1F flare at 07:00, an M1.6/1N flare at 12:53, an M2.3/1N flare at 18:12, a C2.4 flare at 21:24, an M1.8/1N flare at 22:24 and a C6.8 flare at 23:55 UT. April 22: Region 9433 produced an impulsive M3.2/1N flare at 20:44 UT. A strong type II sweep was associated with this 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 was in a possibly geoeffective position on April 23 and could cause unsettled to active conditions on April 26. Forecast The geomagnetic field is expected to be quiet to minor storm on April 25 and quiet to active on April 26. 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 N09W71 0030 AXX 9431 2001.04.17 2 S10W44 0020 HSX 9432 2001.04.18 3 N09W62 0060 CAO 9433 2001.04.18 76 N17E02 1000 FKC beta-gamma-delta 9435 2001.04.19 8 S19W39 0200 DSO 9436 2001.04.21 3 S11E32 0150 CSO 9437 2001.04.21 1 N09E34 0050 HSX 9438 2001.04.24 1 S13E22 0010 AXX Total number of sunspots: 95 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) 2001.04 174.2 (1) 128.0 (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]