Solar Terrestrial Activity Report [Image] Last update May 26, 2001 at 05:25 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update May 1, 2001)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update May 2, 2001)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update May 2, 2001)] [Historical solar and geomagnetic data charts 1954-2001 (last update April 8, 2001)] Recent development The geomagnetic field was quiet to unsettled on May 25. Solar wind speed ranged between 470 and 631 km/sec. Solar flare activity was low. Solar flux was 153.5 (the measurement at 17h UTC was used as the 20h UTC value was slightly enhanced by a flare in region 9468), the planetary A index was 8 (3-hour K indices: 2122 3332, Boulder K indices: 2122 4331). Region 9461 was quiet and stable, as was region 9462. Region 9463 decayed slowly and was mostly quiet. There is still a possibility of an M class flare. Region 9465 was quiet and stable, as were regions 9466 and 9467. Region 9468 decayed slowly but could still produce a minor M class flare. Region 9472 was quiet and stable. A small region rotated into view at the northeast limb but was not numbered by SEC/NOAA. Another, larger, region could rotate into view today at the northeast limb. Flares and CMEs A total of 4 C class events were recorded on May 25. Region 9468 produced a C1.2 flare at 11:19, a C5.2/1F long duration event peaking at 19:37 and a C2.8 flare at 22:10 UTC. A filament eruption in the northwest quadrant began at approximately 02:48 UTC as observed in LASCO EIT images. A slow halo CME was observed in LASCO C3 images during the morning and it is likely that the CME is geoeffective. The background x-ray flux is at the class B4 level. Coronal holes No obvious coronal holes are currently approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to unsettled on May 26-27. A CME could arrive on May 28 and cause unsettled to minor storm conditions. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is fair to 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 no. Location at region numbered sunspots midnight Area Classification Comment 9460 2001.05.14 S24W82 plage 9461 2001.05.15 1 N22W58 0030 HAX 9462 2001.05.17 1 N20W28 0060 HSX 9463 2001.05.18 26 N08W23 0480 EKI 9464 2001.05.19 S09W15 plage 9465 2001.05.20 6 S13W01 0010 BXO 9466 2001.05.21 7 S04W12 0030 CSO 9467 2001.05.21 2 S08E00 0060 HSX 9468 2001.05.21 22 N07E12 0090 DAO 9470 2001.05.22 S16W58 plage 9471 2001.05.23 S13W29 plage 9472 2001.05.23 1 N12E34 0010 HSX Total number of sunspots: 66 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 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) 2000.07 202.3 170.1 119.7 (+1.0) 2000.08 163.0 130.5 118.6 (-1.1) 2000.09 182.1 109.7 116.2 (-2.4) 2000.10 167.4 99.4 114.5 (-1.7) 2000.11 178.8 106.8 (112.5 predicted, -2.0) 2000.12 173.6 104.5 (109.9 predicted, -2.6) 2001.01 166.6 95.6 (106.2 predicted, -3.7) 2001.02 146.6 80.1 (101.8 predicted, -4.4) 2001.03 177.7 114.2 (98.2 predicted, -3.6) 2001.04 177.7 108.2 (97.0 predicted, -1.2) 2001.05 148.6 (1) 106.9 (2) (96.3 predicted, -0.7) 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]