Solar Terrestrial Activity Report [Image] Last update April 3, 2001 at 04:50 UT. Minor update posted at 08:27 UT [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, 2001)] [Solar cycles 1-20] [Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2001)] [Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update April 2, 2001)] [Historical solar and geomagnetic data charts 1954-2000 (last update January 18, 2001)] Recent development The geomagnetic field was unsettled to active on April 2. Solar wind speed ranged between 462 and 625 km/sec. Solar flare activity was very high. Solar flux was 228.0, the planetary A index was 20 (3-hour K indices: 4443 3334, Boulder K indices: 4443 2334). Region 9393 was mostly unchanged as a large and very complex region. Further X class flaring is likely while the region rotates over the west limb during the next couple of days. Region 9395 was quiet and stable. Region 9397 decayed slowly and was quiet. Region 9401 decayed slowly and quietly. Region 9404 was quiet and stable, as were regions 9406 and 9407. Region 9408 was mostly unchanged and quiet, the region could produce M class flares. Region 9412 was quiet and stable. Region 9413 developed slowly and was quiet. New region 9414 rotated into view at the southeast limb. Another new region has emerged near region 9414. A large and bright region is currently rotating into view at the southeast limb, it is capable of producing major flares, perhaps even X flares. Comment added at 08:27 UT on April 3: The large and hot region at the southeast limb was the source of today's X1.1 flare. This region has been quite active for the past week or so producing several CMEs. An M2.7 flare was recorded at 07:03 while an M1.4 flare occurred at 08:18 UT. The above 10 MeV proton event has so far peaked just above the 1000 pfu level. Flares and CMEs A total of 2 C, 3 M and 3 X class events were recorded on April 2. Region 9393 produced an M3.2 flare at 00:28, a C5.5 flare at 04:08, an M1.0 flare at 05:28, a C8.5/1F flare at 09:26, an M1.9 flare at 09:52, an impulsive X1.4/1B flare at 10:14 (no obvious CME was associated with this event), a long duration X1.1 event peaking at 11:36 (a CME was observed off the west limb but is not likely to have been geoeffective), and finally an extremely energetic flare, an X17.1 event peaking at 21:51 UT. Type II and IV sweeps were recorded and an extremely fast full halo CME was observed. Had this event occurred 3-5 days ago the CME would likely have reached Earth within 24 hours. With the source of the CME near the west limb it is more difficult to estimate the actual arrival of the solar wind shock, could be anytime on April 4. A proton event is currently in progress and the above 10 MeV proton flux has so far reached the 300 pfu level (fairly "disappointing" for a flare of X10+ magnitude). The X17 flare ranks second among the most powerful flares observed over the last 25 years. A long duration X1.1 event peaked just before 04h UT on April 3. The background x-ray flux is at the class C5 level. Coronal holes A coronal hole in the northern hemisphere was in a geoeffective position on March 31 and April 1 and could cause unsettled to active conditions on April 3-4. Forecast The geomagnetic field is expected to be quiet to active on April 3 and quiet to severe storm on April 4. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor to useless. 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 9393 2001.03.21 40 N16W70 1810 FKC beta-gamma-delta 9394 2001.03.22 N08W72 plage 9395 2001.03.23 1 S13W60 0020 HSX 9397 2001.03.24 9 S08W48 0080 CAO 9401 2001.03.25 13 N21W52 0140 CAO 9402 2001.03.25 N20W83 plage 9403 2001.03.26 S15W35 plage 9404 2001.03.27 12 S05W17 0050 DSO 9405 2001.03.28 S13W86 plage 9406 2001.03.28 2 N27E04 0200 HAX 9407 2001.03.28 2 N12W01 0080 HSX 9408 2001.03.28 24 S09W31 0310 EKI beta-gamma 9410 2001.03.30 S36E13 plage 9411 2001.03.30 N08E22 plage 9412 2001.03.30 2 S13E38 0040 HSX 9413 2001.04.01 7 N10W30 0030 DSO 9414 2001.04.02 1 S21E58 0020 HSX Total number of sunspots: 113 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 1999.12 169.8 84.6 111.1 (+0.1) 2000.01 158.1 90.1 112.9 (+1.8) 2000.02 174.1 112.9 116.8 (+3.9) 2000.03 208.2 138.5 119.9 (+3.1) 2000.04 184.2 125.5 120.8 (+0.9) cycle 23 sunspot max. 2000.05 184.9 121.6 119.0 (-1.8) 2000.06 179.8 124.9 118.7 (-0.3) 2000.07 202.3 170.1 119.8 (+1.1) 2000.08 163.0 130.5 118.6 (-1.2) 2000.09 182.1 109.7 116.2 (-2.4) 2000.10 167.4 100.1 (114.6 predicted, -1.6) 2000.11 178.8 106.5 (112.6 predicted, -2.0) 2000.12 173.6 104.5 (110.1 predicted, -2.5) 2001.01 166.6 95.7 (106.3 predicted, -3.8) 2001.02 146.6 80.1 (101.9 predicted, -4.4) 2001.03 177.7 114.2 (98.4 predicted, -3.5) 2001.04 242.8 (1) 17.5 (2) (97.1 predicted, -1.3) 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 25-40% 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 noted in solar links. Comments and suggestions are always welcome. ------------------------------------------------------------------------ Do you know about the survey which will be held this Summer among the listeners of WWV and WWVH? There is information about this survey at 16 minutes past the hour on WWV and at 47 minutes past the hour on WWVH. If you want to participate send an email with your name and address. ------------------------------------------------------------------------ [DX-Listeners' Club] [DX News] [StudyWeb]