Solar Terrestrial Activity Report [Image] Last update April 16, 2001 at 04:05 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 15. Solar wind speed ranged between 450 and 572 km/sec. Solar flare activity was high. Solar flux was 134.2, the planetary A index was 13 (3-hour K indices: 3432 4323, Boulder K indices: 3432 3322). Region 9415 was mostly unchanged and may be capable of producing another major flare before the region rotates too far behind the west limb. Region 9418 was quiet and stable, the region will rotate off the visible disk early on April 17. Regions 9420, 9422, 9424 and 9426 were quiet and decayed slowly. Region 9427 decayed and could become spotless by the end of the day. Region 9428 decayed into spotless plage. Region 9429 was quiet and stable. A new region has emerged in the southwest quadrant and is developing rapidly early on April 16. Flares and CMEs A total of 7 C and 1 X class events were recorded on April 15. Region 9415 produced a C3.6 flare at 06:14 and a C7.7 flare at 08:45 UT. The region was the source of the second largest flare of solar cycle 23, an impulsive X14.4/2B event at 13:50 UT. Strong type II and IV sweeps were recorded as well. Unfortunately no new LASCO images have become available over the last couple of days, making it difficult to tell if the CME associated with this flare will influence the geomagnetic field. Although the flare occurred near the southwest limb, there is a fair possibility of the CME causing active to minor storm conditions on April 17 or 18. A radiation storm began shortly after the flare. The above 100 MeV proton flux has peaked at the 146 pfu level, while the above 10 MeV flux has so far peaked at 951 pfu. A ground level event was in progress by 15h UT and a polar cap absorption event began a few hours later. The background x-ray flux is at the class B6 level. Coronal holes An isolated coronal hole in the southern hemisphere was in a geoeffective position on April 15 and could cause unsettled to active conditions on April 18. Forecast The geomagnetic field is expected to be quiet to unsettled on April 16 and most of April 17. The CME from the X14 flare on April 15 could reach Earth sometime on April 17 or the first half of April 18 and cause active to minor storm conditions. A coronal stream will likely cause unsettled to active conditions on April 18. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor to useless. 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 9415 2001.04.03 4 S21W87 0350 DKO beta-gamma 9418 2001.04.04 4 N26W72 0170 EAO 9420 2001.04.05 1 S07W59 0020 HRX 9422 2001.04.06 4 S12W30 0020 CSO 9424 2001.04.08 3 S17W62 0020 CRO 9426 2001.04.11 2 S09W16 0010 HSX 9427 2001.04.11 1 S08W64 0020 HSX 9428 2001.04.14 N14W52 plage 9429 2001.04.14 1 N09E50 0120 HSX Total number of sunspots: 20 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) 2001.04 181.0 (1) 91.9 (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]