Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update September 3, 1999 at 03:40 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 2. Solar wind speed ranged between 410 and 487 km/sec. Solar flare activity was low. Solar flux was 157, the planetary A index was 11 (3-hour K indices: 3342 3322, Boulder K indices: 4332 2221). Region 8674 decayed further and was quiet, the region rotated off the visible disk early on September 3. Region 8675 was mostly unchanged and produced the only C flare of the day. Regions 8677 and 8679 were quiet and stable. Region 8681 decayed slowly and was quiet. Region 8682 was quiet and stable. Region 8686 was mostly quiet and stable. New region 8687 emerged in the northwest quadrant near the central meridian. Flares and CMEs Only 2 C flare were recorded on September 2, the first was a C5.3/2F long duration event produced by region 8675. Several events producing coronal mass ejections were observed during the day. First a filament eruption occurred near N20W10 starting at 04:24 UTC. A weak CME was observed over the northwest limb with traces of material in several other directions. Another filament eruption occurred at 10:36 near S20W15 and may have been associated with a CME. A prominence erupted near the southeast limb starting at 13:26 UTC. The associated CME was a partial halo CME but as most of the ejection appears to have occurred behind the limb, there is little chance of any terrestrial impact. Another eruption, a C2.1 flare, occurred just before midnight in region 8679, it was followed by a CME appearing below the south pole and off the southwest limb. September 1: A C2.7 flare from region 8677 at 00:45 UTC was quite interesting. It was accompanied by a small coronal mass ejection. As region 8677 at the time was located near the central meridian and the solar equator, there is a fairly good chance of a direct terrestrial impact sometime on September 4. The background x-ray flux is at the class B5 level. Coronal holes A couple of small coronal holes in the southern hemisphere will be in geoeffective positions September 3-4. They could cause unsettled to active intervals on September 6-7. A larger coronal hole in the northern hemisphere is likely too far to the north to become geoeffective. Forecast The geomagnetic field is expected to be quiet to active on September 3. On September 4 a CME could impact earth and cause unsettled to minor storm conditions. On September 5-6 a couple of CMEs observed on September 2 could reach the earth and cause unsettled to minor storm conditions. On September 6-7 a coronal stream could influence the geomagnetic field causing unsettled to active intervals. Low frequency (below 2 MHz) radio wave propagation along east-west paths over high and upper middle latitudes is generally 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 8674 990820 6 S26W87 0060 CAO 8675 990824 16 N19W42 0070 DSO 8676 990824 N27W43 plage 8677 990825 1 N08W35 0040 HSX 8679 990826 1 S36W28 0000 AXX 8681 990828 13 N21W57 0160 DAO 8682 990829 3 N18E11 0010 CRO 8683 990830 S10W02 plage 8684 990830 S12E09 plage 8685 990831 S08E40 plage 8686 990831 8 S24W23 0010 BXO 8686 990831 6 N11W07 0020 CRO Total number of sunspots: 54 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 84.6 (+2.0) 9903 126.3 69.1 (85.6 predicted, +1.0) 9904 117.2 63.9 (89.3 predicted, +3.7) 9905 148.4 106.3 (94.7 predicted, +5.4) 9906 169.8 137.4 9907 165.6 113.5 9908 170.7 93.7 9909 159.9 (1) 9.0 (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]