Last update issued on May 19, 2003 at 02:55 UTC.
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The geomagnetic field was quiet to unsettled on May 18. Solar wind speed ranged between 383 and 468 km/sec. A slow increase in solar wind speed was observed after 15h UTC as the fairly weak high speed stream from coronal hole CH39 began to dominate the solar wind.
Solar flux measured at 20h UTC on 2.8 GHz was 109. The planetary A
index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.5).
Three hour interval K indices: 22223333 (planetary), 12222333 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight there were 4 spotted regions on the visible disk. Solar flare activity was low. A single C class event was recorded during the day.
Region 10356 reemerged with a few spots.
Region 10357 developed slowly and was mostly quiet. Flare: C1.0 at 10:57 UTC.
Region 10362 was mostly unchanged. There is not much separating opposite polarity spots with an area of negative polarity embedded in the mainly positive polarity trailing spot area.
Spotted regions not numbered by SEC/NOAA:
[S161] A new region emerged in the southwest quadrant on May 18, south of region 10357. Location at midnight: S26W15.
May 16-18: 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 recurrent trans equatorial coronal hole (CH39) was in a geoeffective position on May 15-16. A recurrent trans equatorial coronal hole (CH40) will rotate into a geoeffective position on May 18-20.
Processed SOHO EIT 284 image at 01:06 UTC on May 19. Any black areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to active on May 19 and quiet to unsettled on May 20. A high speed stream from coronal hole CH40 is expected to influence the field from late on May 21 until May 24 and cause unsettled to active conditions with a possibility of occasional minor storm intervals. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor and will likely be very poor until at least May 25. Propagation along north-south paths is fair and is likely to be at least fair until May 25. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: none, Radio Cristal del Uruguay and Cadena Peruana de Noticias were both noted.]
|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|
area was 0080
formerly region S160
|Total spot count:||29||32|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2002.11||168.7||95.5||(84.9 predicted, -5.6)|
|2002.12||157.2||80.8||(80.5 predicted, -4.4)|
|2003.01||144.0||79.5||(77.5 predicted, -3.0)|
|2003.02||124.5||46.2||(72.4 predicted, -5.1)|
|2003.03||131.4||61.5||(66.8 predicted, -5.6)|
|2003.04||126.4||60.0||(61.9 predicted, -4.9)|
|2003.05||112.5 (1)||55.2 (2)||(57.9 predicted, -4.0)|
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.