Solar Terrestrial Activity Report [Image] Last update April 21, 2001 at 03:10 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 20. Solar wind speed ranged between 376 and 426 km/sec. Solar flare activity was moderate. Solar flux was 167.8 (the measurement at 20h UT was flare enhanced, the 17h UT reading has been used instead) , the planetary A index was 8 (3-hour K indices: 3312 2322, Boulder K indices: 3312 2332). Region 9429 was quiet and stable. Region 9431 reemerged with a few spots. Region 9432 did not change significantly and could produce further C class flares. Region 9433 continued to be active and has major flare potential. Region 9434 began to decay and could become spotless within a couple of days. Region 9435 was quiet and stable. A spotted region is rotating into view at the southeast limb. Flares and CMEs A total of 8 C and 2 M class events were recorded on April 20. Region 9433 produced an M1.0/1F long duration event peaking at 05:23, a C1.9 flare at 07:09, a C4.0/1F flare at 19:16 and an M4.1/1F flare at 20:04 UT. None of the flares appeared to be associated with CMEs. Region 9432 generated a C1.5 flare at 08:50 UT. A fast coronal mass ejection was observed mainly off the northeast limb beginning at 11:18 UT in LASCO C3 images, its source was likely in a region behind the northeast limb. The background x-ray flux is at the class B6 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 unsettled on April 21-22. A weak coronal stream based disturbance could start on April 22 and cause unsettled to active conditions. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is poor to 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 9426 2001.04.11 S08W79 plage 9429 2001.04.14 1 N09W18 0050 HSX 9430 2001.04.16 S17W85 plage 9431 2001.04.17 4 S12E15 0030 CSO 9432 2001.04.18 11 N08W06 0050 DAO 9433 2001.04.18 17 N17E52 0700 FHO beta-gamma 9434 2001.04.19 3 N19W38 0030 DSO 9435 2001.04.19 7 S20E14 0030 DAO Total number of sunspots: 43 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) 2001.04 170.4 (1) 106.8 (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]