Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update October 22, 1999 at 02:55 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update October 2, 1999)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update October 2, 1999)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update October 2, 1999)] [Historical solar and geomagnetic data charts 1954-1999] [Experimental solar data chart January 1998-September 1999] Recent development The geomagnetic field was quiet to active on October 21. Solar wind speed ranged between 352 and 527 km/sec. A solar wind shock was observed at 01:30 UTC. This was highly likely related to the arrival of a coronal mass ejection following a filament eruption which started late on October 17 in the southern hemisphere. During most of the day the interplanetary magnetic field was strongly northwards and this resulted in only a few periods where the geomagnetic field was disturbed. After 23h UTC the IMF swung very strongly southwards and this has resulted in severe storming early on October 22. From 02:30 UTC the southward swing has become very impressive. Isolated extremely severe (K index 9) intervals would not be a surprise today and the planetary A index for October 22 could surpass 100. Solar flare activity was low. Solar flux was 158.5, the planetary A index was 15 (3-hour Kp indices: 3422 2334, Boulder K indices: 3422 2334). Region 8728 rotated off the visible disk. Region 8731 decayed slowly and is capable of minor M class flaring. Region 8732 was mostly unchanged and could produce further C flares and perhaps an M flare before rotating over the west limb on October 23. Region 8734 was quiet and stable. Regions 8735 and 8736 decayed into spotless plage. Region 8737 developed further and has minor M class flaring potential. Region 8738 was quiet and stable. Region 8739 should produce further C flares and has minor M class flaring potential. An active region is rotating into view at the southeast limb. An active region just behind ther northeast limb should rotate into view in 2-3 days. Flares and CMEs 11 C flares were recorded on October 21. Regions 8732, 8737, 8739 produced 2 C flares each. The remaining flares were optically unaccounted, among them a C6.1 impulsive flare at 19:55 UTC. Region 8737 produced a moderate duration C3.0 flare peaking at 04:17 UTC. LASCO EIT images indicate there may have been a small coronal mass ejection associated with the flare. If there was it could impact the earth on October 24. The background x-ray flux is at the class C1 level. Coronal holes A well placed coronal hole in the northern hemisphere will move into a geoeffective position on October 21-22. Forecast The geomagnetic field is expected to be active to very severe storm (Kp=8) on October 22. A coronal stream will cause the geomagnetic field to reach unsettled to minor storm levels from late on October 24 to October 26. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally 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 8728 991008 1 N22W94 0080 HAX 8729 991009 N16W88 plage 8731 991011 28 N12W67 0320 EAI 8732 991012 15 N21W76 0160 FAI 8734 991015 1 N18W59 0020 HSX 8735 991016 N18W32 plage 8736 991017 S25W19 plage 8737 991019 28 S15W12 0170 EAI beta-gamma 8738 991020 3 N17E13 0020 CSO 8739 991020 8 S12E58 0130 DAO Total number of sunspots: 84 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 9807 114.0 66.6 65.5 (+3.0) 9808 136.0 92.2 67.8 (+2.3) 9809 138.3 92.9 69.5 (+1.7) 9810 117.2 55.5 70.5 (+1.0) 9811 140.1 74.0 73.0 (+2.5) 9812 150.1 81.9 77.9 (+4.9) 9901 140.6 62.0 82.6 (+4.7) 9902 141.9 66.3 84.6 (+2.0) 9903 126.3 68.8 83.8 (-0.8) 9904 117.2 63.9 (84.9 predicted, +1.1) 9905 148.4 106.4 (89.5 predicted, +4.6) 9906 169.8 137.4 (93.6 predicted, +4.1) 9907 165.6 113.5 9908 170.7 93.7 9909 135.7 70.6 9910 160.3 (1) 109.6 (2) 1) Running average based on the daily 20:00 UTC solar flux value at 2800 MHz.. 2) Unofficial, accumulated value. The official value 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 in solar links. Comments and suggestions are always welcome. ------------------------------------------------------------------------ [DX-Listeners' Club] [DX News] [StudyWeb]