Solar Terrestrial Activity Report [Planetary A Index, Solar Flux and SEC sunspot number] Last update December 25, 1999 at 04:55 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 to active on December 24. Solar wind speed ranged between 328 and 501 km/sec, generally slowly increasing all day. The interplanetary magnetic field was quite strong during the first half of the day and, at times, swung strongly southwards. Normally minor storming would have been expected but geomagnetic activity failed to exceed the active level. Solar flare activity was low. Solar flux was 182.4, the planetary A index was 10 (3-hour Kp indices: 2334 2212, Boulder K indices: 2234 2222). Region 8798 decayed slowly, further C class flares are possible before the region rotates over the west limb on December 26. Region 8803 decayed slowly and will rotate off the visible disk today. 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 could produce C flares. Region 8808 once again decayed into spotless plage. New region 8809 rotated into view at the northeast limb. New region 8810 rotated partly into view at the northeast limb. This region was very active during the day producing many C flares, minor M class flares are possible. Flares and CMEs 17 C flares were recorded on December 24. Region 8806 produced a C3.1 flare at 05:33 UTC and a C1.7 flare at 15:49 UTC. Region 8798 was the source of a C2.4 flare at 16:47 and a C4.4 flare at 18:34 UTC. The majority of the remaining flares were generated by region 8810 with the most energetic event a C8.4 flare at 09:34 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 B7 level. Coronal holes No obvious coronal holes are currently approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to minor storm on December 25 as at least one CME is likely to impact Earth. Major storm intervals are possible. 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 8798 991213 9 S13W73 0280 DAO beta-gamma 8800 991214 N10W74 plage 8803 991216 3 S13W80 0000 BXO 8804 991216 2 S18W25 0300 HHX 8806 991217 48 N20W14 1050 FKC beta-delta 8807 991218 10 N12W11 0020 BXO 8808 991219 S18W60 plage 8809 991224 3 N21E67 0010 BXO 8810 991224 1 N35E75 0030 HSX Total number of sunspots: 79 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 174.5 (1) 98.0 (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]