Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 11, 1999 at 03:00 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 10. Solar wind speed ranged between 428 and 593 km/sec, slowly increasing throughout the day under the influence of a coronal stream. Solar flare activity was very low. Solar flux was 122, the planetary A index was 15 (3-hour K indices: 2343 4333, Boulder K indices: 2333 3233). Region 8689 decayed into spotless plage. Region 8690 was mostly quiet and stable, however, the region is fairly hot and could produce C flares and occasional minor M flares. Region 8691 was quiet and stable. Region 8692 developed several new spots and produced a few sub flares. Minor M class flares are possible. Regions 8693 and 8694 were quiet and stable. New region 8695 rotated into view at the northeast limb. Flares and CMEs There was no flaring of interest on September 10. Several coronal mass ejections originating on the back side of the sun have been observed over the last couple of days, two of the CMEs were unusually fast. The background x-ray flux is at the class B2-B3 level. Coronal holes A coronal hole in the northern hemisphere was in a geoeffective position on September 8-10. A moderately large and well placed coronal hole in the southern hemisphere will rotate into 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 unsettled to active on September 11 with a chance of isolated minor storm intervals due to a coronal stream. 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 S08W63 plage 8688 990903 S24W79 plage 8689 990905 N20W74 plage 8690 990906 14 N13E20 0060 DSO 8691 990907 2 S31W69 0000 AXX 8692 990907 22 S27E36 0320 EAI beta-gamma 8693 990907 6 N13E37 0050 CSO 8694 990908 2 S17W34 0010 AXX 8695 990910 1 N19E73 0020 HSX Total number of sunspots: 47 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 127.8 (1) 37.1 (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]