Last update issued on April 16, 2003 at 02:30 UTC. Minor update posted at 12:24 UTC.
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[Solar cycles 21-23 (last update April 2, 2003)]
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The geomagnetic field was quiet to minor storm on April 15. Solar wind speed ranged between 519 and 630 km/sec under the influence of a high speed stream from coronal hole CH32.
Solar flux measured at 20h UTC on 2.8 GHz was 100.5. The planetary A
index was 22 (STAR Ap - based on the mean of three hour interval ap indices: 23.3).
Three hour interval K indices: 44454223 (planetary), 44454323 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight there were 3 spotted regions on the visible disk. Solar flare activity was very low.
Region 10330 was quiet and is rotating out of view at the northwest limb.
Region 10334 decayed slowly and quietly.
Region 10335 decayed slowly and could become spotless today.
Comment added at 12:24 UTC on April 16, 2003: The geomagnetic field has become very disturbed with several high latitude magnetometers recording very severe storm levels after 10h UTC. Minor storming has been observed at all other latitudes. The cause of the increased disturbance levels is an intensification of the current high speed stream.
A new region has emerged with a few spots east of region 10334.
April 13-15: No obviously geoeffective CMEs observed.
Coronal hole history (since late October 2002)
Compare today's report with the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
A large trans equatorial southern hemisphere coronal hole (CH32) was in a geoeffective position on April 11-13, CH32 has become smaller over the last rotation. A small coronal hole (CH33) in the southern hemisphere will likely rotate into a geoeffective position on April 18. A coronal hole (CH34) in the northern hemisphere will rotate into a geoeffective position on April 18-19.
Processed SOHO EIT 284 image at 15:06 UTC on April 15. Any black areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to active on April 16-17 due to a high speed stream from coronal hole CH32, quiet to unsettled is likely on April 18-20 while high speed coronal hole streams will cause unsettled to active conditions on April 21-22. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is likely to remain very poor until at least April 19. Propagation along north-south paths is fair and is expected to remain fair until at least April 18. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Cadena Peruana de Noticias.]
|Coronal holes (1)||Coronal mass ejections (2)||M and X class flares (3)|
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.
Compare to the previous day's image.
Data for all numbered solar regions according to the Solar Region Summary provided by SEC/NOAA. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SEC or where SEC has observed no spots.
|Solar region||Date numbered||SEC
|Location at midnight||Area||Classification||Comment|
classification was HSX
classification was DRO
at midnight, area 0020
|Total spot count:||14||6|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2002.10||167.0||97.5||(91.0 predicted, -3.6)|
|2002.11||168.7||95.0||(85.7 predicted, -5.3)|
|2002.12||157.2||81.6||(81.3 predicted, -4.4)|
|2003.01||144.0||79.5||(78.3 predicted, -3.0)|
|2003.02||124.5||46.2||(73.3 predicted, -5.0)|
|2003.03||131.4||61.5||(67.6 predicted, -5.7)|
|2003.04||122.2 (1)||46.4 (2)||(62.7 predicted, -4.9)|
1) Running average based on the daily 20:00 UTC observed 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. All time references are to the UTC day. Comments and suggestions are always welcome.