Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update December 24, 1999 at 02:10 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update December 2, 1999)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update December 2, 1999)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update December 2, 1999)] [Historical solar and geomagnetic data charts 1954-1999] [Experimental solar data chart January 1998-September 1999] Recent development The geomagnetic field was quiet on December 23. Solar wind speed ranged between 276 and 330 km/sec. Solar wind density started a gradual increase after 05h UTC and has been well above average since noon on Dec.23. The interplanetary magnetic field strengthened significantly and particularly late in the day. The source of the disturbance is not certain, however, a CME from an erupting filament is most likely based on the available solar wind parameters. Minor or major storming will be possible later today. Solar flare activity was low. Solar flux was 198.4, the planetary A index was 5 (3-hour Kp indices: 0001 2221, Boulder K indices: 0001 1202). Region 8798 decayed slowly and was mostly quiet. The region could produce a minor M class flare. Region 8803 decayed slowly. Both region 8798 and 8803 will rotate off the visible disk over the next 2-3 days. Region 8804 was quiet and stable. Region 8806 is a large, complex region capable of producing major flares. A major flare is possible. Region 8807 is unstable and could produce C flares and minor M flares. Region 8808 reemerged with a single spot, however, the region appears to be spotless again early on Dec.24. An active region at the northeast limb is rotating onto the disk. Flares and CMEs 8 C flares were recorded on December 23. Region 8803 produced a C4.3 flare at 00:10 UTC and a C3.1 flare at 13:54 UTC. December 22: Region 8806 was the source of a major flare, an impulsive M5.3/1B event at 19:04 UTC. A full halo CME was observed in LASCO C2 starting at 19:31 UTC. There is a high probability (at least 90%) that the CME will impact Earth on December 25 (most likely) or 26. Region 8807 generated an M1.8/2B event at 02:16 UTC. The flare was preceded by an eruption in an unspotted region north of region 8806. This eruption was associated with a moderately strong type II sweep and a coronal mass ejection mainly over the north pole. Traces of material could be seen over most of the western and eastern hemisphere as well making this at least a partial halo CME. A terrestrial impact is likely on December 25 but could be overtaken be the faster CME observed later in the day. The background x-ray flux is at the class B8 level. Coronal holes No obvious coronal holes are currently approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to major storm on December 24. There is a high probability of at least one CME impact on Dec.25 or 26, likely resulting in minor to severe storming. 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 Location region numbered no. at Area Classification Comment sunspots midnight 8798 991213 13 S14W59 0370 DKO beta-gamma 8800 991214 N10W61 plage 8802 991216 S23W87 plage 8803 991216 4 S14W69 0030 DSO 8804 991216 1 S18W11 0250 HHX 8806 991217 28 N19W01 1100 FHC beta-gamma-delta 8807 991218 5 N11E02 0020 CAO 8808 991219 1 S18W47 0010 HAX Total number of sunspots: 52 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 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 83.8 (-0.8) 9904 117.2 63.7 85.4 (+1.6) 9905 148.4 106.4 90.4 (+5.0) 9906 169.8 137.7 (92.5 predicted, +2.1) 9907 165.6 113.5 (94.0 predicted, +1.5) 9908 170.7 93.7 (98.9 predicted, +4.9) 9909 135.7 70.6 9910 164.8 116.4 9911 191.5 132.7 9912 174.1 (1) 93.2 (2) 1) Running average based on the daily 20:00 UTC solar flux measurement at 2800 MHz by DRAO. 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]