Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 12, 1999 at 03:35 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update September 1, 1999)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update September 1, 1999)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update September 1, 1999)] [Historical solar and geomagnetic data charts 1954-1999] Recent development The geomagnetic field was quiet to active on September 11. Solar wind speed ranged between 423 and 569 km/sec, peaking near 06h UTC and slowly decreasing after then. A solar wind shock was observed at ACE at 03:20 UTC with an abrupt increase in solar wind speed from 410 to 500 km/sec. This disturbance should reach the earth at approximately 04:10 UTC and could cause unsettled to minor storm conditions. Solar flare activity was low. Solar flux was 122.5, the planetary A index was 10 (3-hour K indices: 4322 2222, Boulder K indices: 4321 2112). Region 8690 developed several new spots but remained mostly quiet. The region could produce C flares and occasional minor M flares. Region 8691 decayed into spotless plage. Region 8692 decayed slowly and is unlikely to produce other than occasional C flares. Regions 8693 was quiet and stable. Region 8694 decayed into spotless plage. Region 8695 was quiet and stable. New region 8696 emerged in the northwest quadrant. New region 8697 emerged in the southwest quadrant near the central meridian. New region 8698 rotated into view at the southeast limb. New region 8699 emerged in the northeast quadrant near region 8693 and has initially developed very quickly. The region could already be capable of M class flaring. Flares and CMEs An optically unaccounted C1 flare was the only flare of the day. Region 8699 produced a couple of sub flares late in the day. A large filament erupted at 00:12 UTC on September 12 in the southwest quadrant producing a CME off the southwest limb. The background x-ray flux is at the class B4 level. Coronal holes A moderately large and well placed coronal hole in the southern hemisphere was in a geoeffective position on September 10-12. A coronal hole in the northern hemisphere could move into a geoeffective position on September 12 or 13. Forecast The geomagnetic field is expected to be quiet to active on September 12, possibly with minor storm intervals because of a CME impact. Another coronal stream should arrive on September 13 and cause unsettled to minor storm conditions, possibly with isolated major storm intervals. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally 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 no. Location at region numbered sunspots midnight Area Classification Comment 8685 990831 S08W76 plage 8689 990905 N20W87 plage 8690 990906 23 N14E06 0100 DSI 8691 990907 S31W82 plage 8692 990907 16 S27E23 0270 EAO 8693 990907 5 N13E23 0050 CSO 8694 990908 S17W47 plage 8695 990910 1 N20E60 0040 HSX 8696 990911 2 N14W48 0010 BXO 8697 990911 3 S20W06 0010 BXO 8698 990911 2 S16E64 0010 AXX 8699 990911 13 N21E29 0030 DRO Total number of sunspots: 65 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 (85.0 predicted, +0.4) 9904 117.2 63.9 (88.0 predicted, +3.0) 9905 148.4 106.4 (93.4 predicted, +5.4) 9906 169.8 137.4 9907 165.6 113.5 9908 170.7 93.7 9909 127.3 (1) 41.9 (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]