Solar Terrestrial Activity Report [Image] Last update April 17, 2001 at 03:20 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 April 8, 2001)] Recent development The geomagnetic field was quiet to unsettled on April 16. Solar wind speed ranged between 387 and 536 km/sec. Solar flare activity was moderate. Solar flux was 123.4 (the lowest value since October 1999), the planetary A index was 7 (3-hour K indices: 3211 2323, Boulder K indices: 2211 2313). Region 9418 was quiet and stable and has rotated off the visible disk. Region 9420 was quiet and stable, the region is spotless early on April 17. Region 9422 was quiet and stable. Regions 9424 and 9426 decayed slowly and were quiet, no spots are visible early on April 17. Region 9427 was quiet and stable, the region has rotated out of view. Region 9429 was quiet and stable. New region 9430 emerged in the southwest quadrant. The northeast limb is brightening in response to the approach of old region 9393. A new region is emerging near the southeast limb. Flares and CMEs A total of 4 C and 1 M class events were recorded on April 16. Region 9415 produced a C3.7 flare at 07:06 UT. The remainder of the flares, including an M1.1 flare at 06:22 UT, were optically unaccounted. April 15: Region 9415 was the source of the second largest flare of solar cycle 23, an impulsive X14.4/2B event at 13:50 UT. Strong type II and IV sweeps were recorded as well. There is a fair possibility that the associated CME will cause active to minor storm conditions on April 17 or 18. A filament eruption in the southeast quadrant near the central meridian was in progress in LASCO EIT images by 01:26 UT (the event probably started approximately an hour earlier). A halo CME was observed in LASCO C3 at 01:42 UT and could reach Earth late on April 17, possibly ahead of the CME associated with the X14 flare. The background x-ray flux is at the class B5 level. Coronal holes An isolated coronal hole in the southern hemisphere was in a geoeffective position on April 15 and could cause unsettled to active conditions on April 18. An isolated coronal hole in the northern hemisphere will rotate into a possibly geoeffective position on April 19. Forecast The geomagnetic field is expected to be quiet to unsettled early on April 17. The CME from the X14 flare on April 15 could reach Earth after noon on April 17 and cause active to minor storm conditions. A coronal stream will likely cause unsettled to active conditions on April 18. 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 no. Location at region numbered sunspots midnight Area Classification Comment 9418 2001.04.04 5 N27W84 0120 EAO 9420 2001.04.05 1 S06W71 0020 HRX 9422 2001.04.06 4 S12W43 0010 CSO 9424 2001.04.08 4 S16W72 0020 CRO 9426 2001.04.11 5 S08W27 0020 CSO 9427 2001.04.11 2 S06W79 0020 HSX 9428 2001.04.14 N14W65 plage 9429 2001.04.14 1 N09E36 0090 HSX 9430 2001.04.16 5 S16W33 0030 DRO Total number of sunspots: 27 Monthly solar data Month Average solar International sunspot Smoothed sunspot flux number number 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 (115.4 predicted, -0.8) 2000.11 178.8 106.5 (114.2 predicted, -1.2) 2000.12 173.6 104.5 (111.7 predicted, -2.5) 2001.01 166.6 95.7 (108.0 predicted, -3.7) 2001.02 146.6 80.1 (103.5 predicted, -4.5) 2001.03 177.7 114.2 (100.0 predicted, -3.5) 2001.04 177.4 (1) 95.5 (2) (98.8 predicted, -1.2) 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]