Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update August 21, 1999 at 04:30 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update August 2, 1999)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update August 2, 1999)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update August 2, 1999)] [Historical solar and geomagnetic data charts 1954-1999] Recent development The geomagnetic field was unsettled to minor storm on August 20. Solar wind speed ranged between 557 and 722 km/sec. Solar wind data indicate that the CME observed on August 17 arrived near 02h UTC mixed with the coronal stream. Solar flare activity was high. Solar flux was 151.6, the planetary A index was 33 (3-hour K indices: 3555 5433, Boulder K indices: 3544 4333). Region 8668 was mostly quiet but could produce isolated C flares and perhaps even a minor M class flare. The region appears to be slowly decaying. Region 8671 decayed into spotless plage. Region 8672 decayed and could become spotless in a day or two. Region 8673 was mostly quiet and stable. New region 8674 rotated into view at the southeast limb and was very active. The corona above the region is very hot and further M flares are likely. Isolated X class flares would not be a surprise either. Flares and CMEs A total of 5 C class events (all from regions at or near the southeast limb) and 3 M flares were observed on August 20. Region 8674 was the origin of all the M flares. The first was a very long duration M1.8 event peaking at 14:18 UTC. Then an impulsive M1.2 flare was observed at 18:29 UTC, it was accompanied by a strong type II sweep. A slow moving coronal mass ejection was observed off the southeast limb. At 23:08 UTC region 8674 produced an impulsive major M9.8/1N flare. A moderately strong type II sweep was recorded and a CME was observed over the east limb. At almost the same time a large filament at a high latitude in the northwest quadrant erupted and a CME was observed over the north pole. The background x-ray flux is at the class C1 level. Coronal holes No obvious coronal holes are currently approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to unsettled on August 21-22, possibly with isolated active intervals. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is very poor to 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 8665 990811 S26W53 plage 8667 990812 N24W33 plage 8668 990813 12 N22W11 0290 CKO 8669 990814 S21W39 8670 990815 S12W88 plage 8671 990815 S10W86 plage 8672 990818 6 N16W31 0020 CRO 8673 990819 2 S19E66 0280 HHX 8674 990820 5 S24E66 0180 EKO Total number of sunspots: 25 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 62.4 82.6 (+4.7) 9902 141.9 66.1 (85.6 predicted, +3.0) 9903 126.3 69.1 (87.6 predicted, +2.0) 9904 117.2 63.9 (91.2 predicted, +3.6) 9905 148.4 106.3 9906 169.8 137.4 9907 165.6 113.5 9908 153.4 (1) 79.8 (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]