Solar Terrestrial Activity Report [Image] Last update April 17, 2002 at 02:00 UTC. Last minor update posted at 15:25 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update 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 16. Solar wind speed ranged between 318 and 352 km/sec. Solar flare activity was moderate. Solar flux was 195.7, the planetary A index was 10 (3-hour K indices: 2331 2332, Boulder K indices: 2231 2222). Region 9896 was quiet and stable and will rotate over the southwest limb early on April 18. Region 9899 was quiet and stable. Region 9901 decayed slowly and quietly and had rotated out of view by the end of the day. Region 9902 decayed slowly and quietly. Region 9903 decayed and was spotless by late afternoon. Region 9905 was mostly unchanged as it rotated onto the southwest limb. Region 9906 developed again and has a strong magnetic delta structure. A major flare is possible anytime. Region 9907 decayed further and was quiet. No significant flares are expected from this region. Region 9909 was quiet. The main penumbra split into two smaller spots. Region 9910 was quiet and stable. Comment added at 09:16 UTC on April 17: Region 9906 produced a long duration M2.6 event peaking at 08:24 UTC. This event may have been a proton flare as well. The leading edge of the associated CME was observed in LASCO C2 images from 08:26 UTC above the southwest limb. Comment added at 10:17 UTC: The CME mentioned above will likely arrive at the Earth on April 19 and cause active to major storm conditions. Comment added at 10:35 UTC: A strong solar wind shock was observed at ACE at 10:27 UTC. The interplanetary magnetic field is initially northwards. If the IMF swings fully southwards we could see major geomagnetic storming. Comment added at 12:18 UTC: LASCO C3 images confirm that the above M2 event was accompanied by a full halo CME. A moderate geomagnetic disturbance is currently in progress. The interplanetary magnetic field swung strongly southwards just before 11h UTC and was mostly southwards until about 12h UTC. A strong sudden impulse was observed at Kiruna at 11:06 UTC. Solar wind speed is currently near 500 km/sec. Comment added at 15:25 UTC: The interplanetary magnetic field swung very strongly southwards at 15h UTC and this could cause the current geomagnetic disturbance to intensify to severe storm level. The geomagnetic field has been at major storm level since the arrival of the CME. A proton flux enhancement is currently in progress and there is a chance of a minor proton event starting later today. Flares and CMEs A total of 4 C and 1 M class events were recorded on April 16. Region 9904 produced a C2.5 flare at 02:19 and a C9.3 flare at 10:44 while at the southwest limb. Region 9893 at the northwest limb generated an M2.5 flare at 13:19 and a C2.9 flare at 15:40 UTC. April 15: Region 9906 was the source of a long duration M1.2 event peaking at 03:55 UTC. This event was associated with a nice full halo CME. LASCO C2 images show the first glimpse of this CME at 03:50 UTC. The CME will impact the Earth, probably sometime between early morning and midnight on April 17, and could cause active to major geomagnetic storm conditions. The background x-ray flux is at the class B9 level. Coronal holes No obvious coronal holes are currently approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to unsettled early on April 17. A solar wind shock is likely sometime during the day and active to major storm conditions are possible following the arrival of the solar storm. 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 Location region numbered no. at Area Classification Comment sunspots midnight 9895 2002.04.05 N06W85 plage 9896 2002.04.05 1 S10W74 0090 HSX 9898 2002.04.06 S18W67 plage 9899 2002.04.06 2 N18W58 0140 CSO 9901 2002.04.07 3 N21W86 0270 HKX 9902 2002.04.07 5 N12W42 0070 CSO 9903 2002.04.08 2 N17W25 0010 AXX now spotless 9905 2002.04.10 3 S15W83 0050 DRO 9906 2002.04.11 27 S15W28 0590 EKI beta-gamma-delta 9907 2002.04.11 23 S03E07 0170 EAO 9908 2002.04.12 N05W83 plage 9909 2002.04.14 2 N11E42 0120 HAX 9910 2002.04.15 4 S20E37 0030 CSO Total number of sunspots: 72 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) 2002.04 207.5 (1) 117.8 (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]