Solar Terrestrial Activity Report [Image] Last update April 11, 2002 at 04:25 UTC. [Solar and geomagnetic data - last 4 weeks (updated daily)] [Solar wind and electron fluence charts (updated daily)] [Solar cycles 21-23 (last update April 2, 2002)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2002)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update April, 2002)] [Historical solar and geomagnetic data charts 1954-2001 (last update January 12, 2002)] Recent development The geomagnetic field was quiet to unsettled on April 10. Solar wind speed ranged between 297 and 347 km/sec. An increase in wind speed to above 400 km/sec has been observed early on April 11. Solar wind density was elevated all day on April 10. Solar flare activity was high. Solar flux was 194.3, the planetary A index was 7 (3-hour K indices: 1013 3332, Boulder K indices: 0112 2322). Region 9887 rotated quietly over the northwest limb. Region 9888 was spotless all day and rotated off the visible disk. Region 9893 did not change significantly and remains capable of producing M class flares. Region 9896 was quiet and stable. Region 9897 decayed and was spotless by the end of the day. Region 9898 was quiet and stable but could become spotless today. Region 9899 did not change much and could produce occasional minor M class flares. Region 9900 lost its magnetic delta and several spots. Many new spots were observed late in the day and the region appears to be developing again. A minor M class flare is possible. Region 9901 was quiet and stable (no distinct separation from region 9893 can be observed). Regions 9902 and 9903 were mostly quiet and stable. Region 9904 had its main penumbra splitting into several smaller parts, the region was quiet. New region 9905 emerged in the southeast quadrant near the central meridian. SEC/NOAA failed to number a new rapidly emerging region in the southeast quadrant. Another spotted region is rotating into view at the southeast limb. Flares and CMEs A total of 7 C and 2 M class events were recorded on April 10. Region 9899 generated a C5.6 flare at 00:59, a C2.4 flare at 03:55, a C4.3/1F flare at 06:50 and an M1.6/1N flare at 19:07 UTC. The M flare was associated with a weak type II radio sweep and a small CME. Region 9900 was the source of a C3.2 flare at 22:42 UTC. Region 9893 produced a C4.2 flare at 15:41 and an impulsive major M8.2 flare at 12:31 UTC. The center of the M flare was located where the trailing magnetic delta structure was (a the time nearly over the central meridian). A fairly small and slow halo CME was observed in LASCO images from 13:27 UTC. This CME was best defined over the northeast quadrant and was faint elsewhere. The CME appeared to be a full halo CME in both the differencing movies and in LASCO C3 images. The background x-ray flux is at the class C1 level. Coronal holes No obvious coronal holes are currently approaching geoeffective positions. Forecast The geomagnetic field is expected to be quiet to unsettled on April 11-12 and quiet to active, possibly with minor storm intervals, on April 13 with the arrival of the CME observed after the major flare in region 9893 on April 10. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is fair. 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 9887 2002.03.29 2 N03W93 0060 CAO 9888 2002.03.29 1 S13W86 0010 AXX actually spotless 9889 2002.03.31 S20W84 plage 9892 2002.04.02 N05W45 plage 9893 2002.04.03 20 N19W14 0300 EKI beta-gamma area too small 9894 2002.04.05 N14W74 plage 9895 2002.04.05 N06W07 plage 9896 2002.04.05 1 S11E08 0110 HSX 9897 2002.04.06 2 S02W59 0030 CSO now spotless 9898 2002.04.06 1 S19E12 0010 AXX 9899 2002.04.06 9 N18E22 0220 DAO 9900 2002.04.07 18 S29W32 0110 ESI beta-gamma 9901 2002.04.07 19 N20W02 0190 DAI still thought to be part of region 9893 9902 2002.04.07 3 N13E43 0100 ESO 9903 2002.04.08 4 N19E47 0060 CSO 9904 2002.04.09 6 S16W21 0050 CSO 9905 2002.04.10 4 S17E04 0040 CSO Total number of sunspots: 90 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 2001.02 146.6 80.6 104.0 (-4.7) 2001.03 177.7 113.5 104.8 (+0.8) 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 (113.3 predicted, -0.8) 2001.11 210.6 106.5 (112.7 predicted, -0.6) 2001.12 235.1 132.2 (109.3 predicted, -3.4) 2002.01 226.6 113.9 (106.0 predicted, -3.3) 2002.02 205.0 108.0 (104.6 predicted, -1.4) 2002.03 179.5 98.1 (100.4 predicted, -4.2) 2002.04 207.6 (1) 70.9 (2) (94.5 predicted, -5.9) 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]