Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 13, 1999 at 04:35 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 unsettled to major storm on September 12. Solar wind speed ranged between 417 and 618 km/sec. A solar wind shock was observed at ACE at 03:22 UTC with an abrupt increase in solar wind speed from 420 to 530 km/sec. The source of the disturbance is uncertain. Solar flare activity was low. Solar flux was 140.8, the planetary A index was 26 (3-hour K indices: 3336 3454, Boulder K indices: 2325 3444). Region 8690 was mostly unchanged and remains capable of producing C flares and occasional minor M flares. Region 8692 did not change significantly and was quiet. C class flares are possible, as is an isolated minor M flare. Region 8693 decayed slowly. Region 8695 was quiet and stable. Regions 8696, 8697 and 8698 decayed into spotless plage. Region 8699 developed further and should continue to produce C flares. M class flares are possible over the next few days. New region 8700 rotated partly into view at the northeast limb. Flares and CMEs A total of 8 C flares (all in the C1-C2 range) were recorded on September 12, 4 were optically unaccounted while region 8699 was the source of the remaining 4 C flares. 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 was in a geoeffective position on September 12-13. Forecast The geomagnetic field is expected to be unsettled to minor storm on September 13-14, possibly with major storm intervals. This activity is caused by the CME impact on September 12 and a coronal stream. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally very 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 S08W89 plage 8690 990906 25 N14W06 0090 DSI 8692 990907 19 S26E11 0230 EAO 8693 990907 2 N13E11 0050 DSO 8694 990908 S17W60 plage 8695 990910 1 N20E48 0030 HSX 8696 990911 N14W61 plage 8697 990911 S20W19 plage 8698 990911 S16E51 plage 8699 990911 17 N21E15 0110 DAI 8700 990912 2 N12E81 0030 HSX Total number of sunspots: 66 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 128.4 (1) 46.1 (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]