Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update October 21, 1999 at 03:05 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update 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 on October 20. Solar wind speed ranged between 339 and 393 km/sec. A solar wind shock was observed at 01:30 UTC on October 21. 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. The shock was quite impressive with solar wind speed increasing abruptly from 350 to 450 km/sec and the interplanetary magnetic field becoming strong to very strong. An initial short lasting and very strong southward excursion of the IMF was observed just after the shock. Should the IMF swing consistently southwards major storming will be likely. Solar flare activity was moderate. Solar flux was 158.8, the planetary A index was 4 (3-hour Kp indices: 0111 2221, Boulder K indices: 0211 2211). Region 8728 was quiet and stable and will rotate off the visible disk today. Region 8731 decayed slowly and is capable of minor M class flaring. Region 8732 was mostly quiet and stable. Region 8734 reemerged with a few spots. Region 8735 was quiet and stable, as was region 8736. Region 8737 developed further and should be capable of C class flaring. New region 8738 emerged in the northeast quadrant. New region 8739 rotated into view at the southeast limb. Flares and CMEs 2 C flares and 1 M flare were recorded on October 20. The only optically correlated flare of the day was the M1.7/1F long duration event produced by region 8731, it peaked at 06:22 UTC. A moderately strong type II sweep was observed as well, as was a coronal mass ejection off most of the west limb. The background x-ray flux is at the class B8 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 unsettled to major storm on October 21-22. A coronal stream will cause the geomagnetic field to reach unsettled to minor storm levels October 24-25. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally fair but could become very poor later today. 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 3 N24W83 0110 CAO 8729 991009 N16W75 plage 8731 991011 45 N14W55 0440 EKI beta-gamma 8732 991012 23 N22W64 0170 FAI 8734 991015 5 N20W46 0010 BXO 8735 991016 3 N18W19 0010 BXO 8736 991017 2 S25W06 0010 AXX 8737 991019 17 S16E01 0070 DAO 8738 991020 2 N16E28 0010 AXX 8739 991020 3 S14E71 0050 CAO Total number of sunspots: 103 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 160.4 (1) 104.6 (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]