Solar Terrestrial Activity Report [Image] Last update April 25, 2002 at 04:05 UTC. [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, 2002)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2002)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update April, 2002)] [Historical solar and geomagnetic data charts 1954-2002 (last update April 13, 2002)] Recent development The geomagnetic field was quiet to unsettled on April 24. Solar wind speed ranged between 453 and 540 km/sec. Solar flare activity was moderate. Solar flux was 176.9, the planetary A index was 7 (3-hour K indices: 3112 2322, Boulder K indices: 3112 2312). Regions 9909 and 9910 both decayed slowly and quietly. Region 9912 lost some its trailing spots but was otherwise mostly unchanged. There is a minor chance of another small M class flare. Region 9913 developed quickly early in the day, then began to decay again. Region 9914 decayed and lost several spots in the leading spots section and nearly all intermediate spots. The negative and positive magnetic polarity areas have separated and the region is currently simple and likely to decay further. Region 9915 developed slowly with the leading penumbra becoming more elongated. Region 9916 decayed slowly with the negative positive magnetic polarity areas drifting apart. Region 9919 was quiet and stable. For unknown reasons SEC/NOAA has included spots belonging to another (not numbered) region in region 9919. In magnetograms these two regions are clearly separate, both having leading positive polarity spots and trailing negative polarity spots. Region 9920 decayed and could become spotless today. Region 9922 developed slowly and quietly. New region 9923 emerged in the southwest quadrant near the equator. New region 9924 emerged in the southeast quadrant near the central meridian on April 23, developed slowly during the first half of April 24, then began to decay and has lost most of its spots early on April 25. The region could soon become spotless again. New region 9925 emerged in the southwest quadrant. Flares and CMEs A total of 14 C and 1 M class events were recorded on April 24. Region 9913 produced a C1.7 flare at 05:48, a C1.4 flare at 06:42 and a C2.0 flare at 10:53 UTC. Region 9924 generated a C1.7 flare at 07:35, a C1.2 flare at 10:25, a C1.0 flare at 13:16 and a C1.9 flare at 17:54 UTC. Region 9912 was the source of a C4.8/1N flare at 16:05 and an impulsive M1.7/1F flare at 21:56 UTC. Region 9916 managed a C2.3 flare at 16:41 UTC. The background x-ray flux is at the class B5 level. Coronal holes A recurrent trans equatorial coronal hole was in a geoeffective position on April 24-25. This coronal hole is not as large as it has been over the last rotations but could cause unsettled to active conditions on April 27-28. Forecast The geomagnetic field is expected to be quiet to unsettled on April 25-26 and unsettled to active on April 27-28. 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 Location region numbered no. at Area Classification Comment sunspots midnight 9909 2002.04.14 1 N07W64 0050 HSX 9910 2002.04.15 1 S21W74 0080 HSX 9911 2002.04.18 S13W56 plage 9912 2002.04.18 15 N09W52 0230 DAO beta-gamma 9913 2002.04.19 13 S16W44 0040 CSO 9914 2002.04.19 23 N04E04 0230 DAO 9915 2002.04.21 11 N12E14 0180 CAO 9916 2002.04.21 19 S18E32 0100 EAO 9917 2002.04.22 S30E19 plage 9918 2002.04.22 N06W26 plage classification wrong, 9919 2002.04.22 6 N12E57 0230 FAO actually two separate regions 9920 2002.04.23 2 S23W15 0020 CSO 9921 2002.04.23 N12E28 plage 9922 2002.04.23 3 N21E40 0010 BXO 9923 2002.04.24 8 S03W31 0020 CRO 9924 2002.04.24 18 S17W07 0060 DAO 9925 2002.04.24 5 S14W21 0040 DSO Total number of sunspots: 125 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 2000.04 184.2 125.5 120.8 cycle 23 sunspot max. 2000.07 202.3 170.1 119.8 2001.02 146.6 80.6 104.0 (-4.7) 2001.03 177.7 113.5 104.8 (+0.8) 2001.04 177.7 107.7 107.5 (+2.7) 2001.05 147.1 96.6 108.6 (+1.1) 2001.06 173.0 134.0 109.8 (+1.2) 2001.07 131.3 82.2 111.7 (+1.9) 2001.08 162.9 106.8 113.6 (+1.8) 2001.09 233.2 150.7 114.1 (+0.5) 2001.10 207.6 125.5 (113.3 predicted, -0.8) 2001.11 210.6 106.5 (112.7 predicted, -0.6) 2001.12 235.1 132.2 (109.3 predicted, -3.4) 2002.01 226.6 113.9 (106.0 predicted, -3.3) 2002.02 205.0 108.0 (104.6 predicted, -1.4) 2002.03 179.5 98.1 (100.4 predicted, -4.2) 2002.04 198.1 (1) 164.9 (2) (94.5 predicted, -5.9) 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 25-45% 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. ------------------------------------------------------------------------ [DX-Listeners' Club] [DX News]