Solar Terrestrial Activity Report [Image] Last update May 24, 2002 at 03:45 UTC. Minor update posted at 07:09 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update May 3, 2002)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update May 3, 2002)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update May 3, 2002)] [Historical solar and geomagnetic data charts 1954-2002 (last update April 13, 2002)] Recent development The geomagnetic field was quiet to severe storm on May 23. Solar wind speed ranged between 382 and 951 km/sec. A coronal stream began to influence the field early in the day. At 10:17 UTC a very strong solar wind shock was observed at SOHO. Solar wind speed initially increased from 390 to 660 km/sec and peaked right after 13h UTC just below the 1000 km/sec (only a few other solar storms during this solar cycle have set up such strong solar winds) mark. The source of this disturbance was a filament/prominence eruption in the southwest quadrant early on May 23. The impressive eruption was associated with a fast full halo CME which used just 31 hours on the transit. The solar storm was complex early on with several rapid changes in velocity and density. The interplanetary magnetic field was strongly or very strongly southwards during three intervals, first between 11 and 12h UTC, then between 15:15 and 17:30 UTC and finally between 19 and 19:45 UTC. After 20h UTC the IMF has been mostly weakly southwards. Solar flare activity was low. Solar flux was 180.3, the planetary A index was 54 (3-hour K indices: 3325 7753, Boulder K indices: 3325 6743). Region 9954 decayed further and could become spotless within a couple of days. Region 9957 decayed further. No polarity intermixing could be observed early on May 24. The inversion line between the positive and negative polarities is well defined, first tracking north, then heading eastwards. Although the flare potential is decreasing slowly, there is still a chance of minor M class flares. Region 9958 decayed slowly and quietly. Region 9960 developed a few spots west of the main penumbra. The main penumbra decreased significantly in size and appears to be splitting into two. If this development continues the magnetic delta structure will soon disappear. Region 9961 developed slowly early in the day and then began to decay slowly. There is currently no magnetic delta structure in this region. Region 9962 was quiet and stable. Region 9963 developed slowly and could produce minor M class flares. Region 9964 decayed and had only a single small spot left by the end of the day, the region could soon become spotless. Region 9965 was quiet and stable. New region 9966 in the northeast quadrant was numbered by SEC/NOAA. The region shares the positive polarity field with region 9963 and the spots could just as well have been boxed with that region. New region 9967 emerged in the northeast quadrant. Comment added at 0709 UTC on May 24: Region 9963 produced an impulsive M1.1 flare at 06:46 UTC. It is not yet known if there was a coronal mass ejection associated with this event. Flares and CMEs A total of 2 C class events were recorded on May 23. Region 9963 produced a C1.2 flare at 20:51 UTC. The background x-ray flux is at the class B5 level. Coronal holes A small coronal hole in the southern hemisphere will rotate into a geoeffective position on May 25 and could cause a mild geomagnetic disturbance on May 28. Forecast The geomagnetic field is expected to be quiet to active on May 24 and quiet to unsettled on May 25-26 Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is 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 Location region numbered no. at Area Classification Comment sunspots midnight 9951 2002.05.12 N12W77 plage 9954 2002.05.15 5 S22W38 0040 DSO 9955 2002.05.15 S13W37 plage 9957 2002.05.16 46 N10W19 0420 EAC 9958 2002.05.17 1 N04W32 0060 HSX 9959 2002.05.17 N10W69 plage 9960 2002.05.18 10 N14E06 0100 DAC beta-delta 9961 2002.05.19 27 S22E22 0290 EAI beta-gamma 9962 2002.05.20 5 N15E21 0030 CSO area too small 9963 2002.05.20 10 N14E36 0420 DHO 9964 2002.05.22 4 S14W05 0010 BXO 9965 2002.05.22 6 S10E48 0060 CSO 9966 2002.05.23 4 N10E34 0010 BXO part of region 9963? 9967 2002.05.23 1 N13E46 0010 AXX Total number of sunspots: 119 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 2000.04 184.2 125.5 120.8 cycle 23 sunspot max. 2000.07 202.3 170.1 119.8 2001.04 177.7 107.7 107.5 (+2.7) 2001.05 147.1 96.6 108.6 (+1.1) 2001.06 173.0 134.0 109.8 (+1.2) 2001.07 131.3 82.2 111.7 (+1.9) 2001.08 162.9 106.8 113.6 (+1.8) 2001.09 233.2 150.7 114.1 (+0.5) 2001.10 207.6 125.5 114.0 (-0.1) 2001.11 210.6 106.5 (114.7 predicted, +0.7) 2001.12 235.1 132.2 (112.5 predicted, -2.2) 2002.01 226.6 113.9 (109.8 predicted, -2.7) 2002.02 205.0 108.0 (108.4 predicted, -1.4) 2002.03 179.5 98.1 (104.2 predicted, -4.2) 2002.04 189.8 120.4 (98.3 predicted, -3.9) 2002.05 176.4 (1) 148.0 (2) (93.8 predicted, -4.5) 1) Running average based on the daily 20:00 UT solar flux value at 2800 MHz. 2) Unofficial, accumulated value based on the Boulder (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% 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 noted in solar links. Comments and suggestions are always welcome. ------------------------------------------------------------------------ [DX-Listeners' Club] [DX News]