Solar Terrestrial Activity Report [Image] Last update April 19, 2001 at 04:30 UT. Minor update posted at 11:43 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 severe storm on April 18. Solar wind speed ranged between 438 and 547 km/sec. Solar flare activity was low. Solar flux was 131.8, the planetary A index was 50 (3-hour K indices: 5774 3412, Boulder K indices: 5553 3332). Region 9429 was quiet and stable. Region 9430 decayed slowly and was spotless by early evening. Region 9431 decayed slowly and was spotless early on April 19. New region 9432 emerged in the northeast quadrant east of region 9429. New region 9433 (old region 9393) rotated into view at the northeast limb. The region is smaller now compared to when we last had a view of it. Occasional M class flares are possible. A new region has emerged in the northwest quadrant. Comment added at 11:43 UT on April 19: Region 9433 produced an M2.0 flare at 11:35 UT. More of the region is rotating into view and the region appears to be fairly complex with a possible magnetic delta inside the leading penumbra. Flares and CMEs A total of 3 C class events were recorded on April 18. A C2.2 flare at 02:14 UT with an associated strong type II sweep has its origin in region 9415 well behind the southwest limb. A radiation storm began shortly after the flare and both a ground level event and a polar cap absorption event were recorded during the day. The above 10 MeV proton flux peaked at 321 pfu. The background x-ray flux is at the class B5 level. Coronal holes An isolated coronal hole in the northern hemisphere was in a possibly geoeffective position on April 19-20. Forecast The geomagnetic field is expected to be quiet to active on April 19 and quiet to unsettled on April 20-21. A weak coronal stream based disturbance could start on April 22. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very 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 9422 2001.04.06 S13W67 plage 9426 2001.04.11 S08W53 plage 9429 2001.04.14 1 N08E09 0080 HSX 9430 2001.04.16 3 S17W59 0020 CRO 9431 2001.04.17 1 S11E36 0000 AXX 9432 2001.04.18 6 N08E20 0030 CRO 9433 2001.04.18 2 N14E74 0150 HHX Total number of sunspots: 13 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) 2001.04 172.0 (1) 100.6 (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]