Last update issued on March 26, 2003 at 03:10 UTC. Minor update posted at 11:57 UTC.
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The geomagnetic field was quiet on March 25. Solar wind speed ranged between 359 and 464 km/sec. Solar wind density has increased slowly since about 09h UTC and the expected high speed stream could arrive within hours.
Solar flux measured at 20h UTC on 2.8 GHz was 108.8. The planetary A
index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 7.4).
Three hour interval K indices: 22212222 (planetary), 12212112 (Boulder).
The background x-ray flux is at the class B2-B3 level.
At midnight there were 7 spotted regions on the visible disk, 1 of the regions has not yet been numbered by SEC/NOAA. Solar flare activity was very low.
Region 10318 developed slightly in the trailing spot section while slow development was observed in the leading spots.
Region 10319 developed slowly and quietly.
Region 10320 decayed slowly and could soon become spotless.
Region 10321 developed several new spots. The trailing penumbra increased its areal coverage. Some polarity intermixing is evident and the region is likely to produce C flares with a minor chance of a small M class flare.
New region 10322 emerged near the northwest limb.
New region 10323 emerged in the southeast quadrant.
Spotted regions not yet numbered by SEC/NOAA:
[S126] A new region emerged in the southwest quadrant on March 24, near the location of spotless region 10316. Location at midnight: S08W21.
Comment added at 11:57 UTC on March 26: Region 10321 continues to developed and a magnetic delta structure is forming at the northwestern edge of the large trailing penumbra. The chance of a minor M class flare is increasing.
A fairly weak disturbance has been in progress since just after midnight. The disturbance may be related to a coronal hole stream. If it is then the disturbance is atypical and has not displayed the usual increase in solar wind speed. The low wind speed (so far, the disturbance could change with higher speeds observed later on today) does not match well with the visual characteristics of CH26 but is consistent with the later than expected arrival of the disturbance.
Otherwise region S126 has become spotless, region 10322 has added several spots and a new region has emerged near the southwest limb during the first half of the day.
March 23-25: 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 well placed, developing and recurrent coronal hole (CH26) mainly in the northern hemisphere was in a geoeffective position on March 22-23. A coronal hole (CH27) in the southern hemisphere will rotate into a geoeffective position on March 24-28, this coronal hole is best defined in the section due west of region 10318.
Processed SOHO EIT 284 image at 01:06 UTC on March 26. Any black areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to minor storm on March 26-27 due to a high speed stream from coronal hole CH26. Quiet to active is likely on March 28-31 due to another high speed stream, this time from CH27. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor, propagation along north-south paths is fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: none, several stations noted including Radio Cristal del Uruguay, Radio Vibración (Venezuela) and Cadena Peruana.]
|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 AXX
at midnight, area 0010
classification was DAI
at midnight, area 0170
classification was BXO
|Total spot count:||29||39|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2002.09||175.8||109.6||(94.7 predicted, -4.0)|
|2002.10||167.0||97.5||(91.2 predicted, -3.5)|
|2002.11||168.7||95.0||(86.0 predicted, -5.2)|
|2002.12||157.2||81.6||(81.6 predicted, -4.4)|
|2003.01||144.0||79.5||(78.6 predicted, -3.0)|
|2003.02||124.5||46.2||(73.6 predicted, -5.0)|
|2003.03||128.0 (1)||88.4 (2)||(67.9 predicted, -5.7)|
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.