Last update issued on May 5, 2003 at 03:20 UTC.
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The geomagnetic field was quiet to unsettled on May 4. Solar wind speed ranged between 350 and 449 km/sec. The apparent onset of a high speed coronal hole stream was observed at ACE near 14:30 UTC. The interplanetary magnetic field has since been mostly northwards or weakly southwards. The major part of the disturbance has not yet arrived.
Solar flux measured at 20h UTC on 2.8 GHz was 142.0. The planetary A
index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.8).
Three hour interval K indices: 32122222 (planetary), 22122222 (Boulder).
The background x-ray flux is at the class B6 level.
At midnight there were 7 spotted regions on the visible disk. Solar flare activity was low. A total of 9 C class events was recorded during the day.
Region 10345 decayed slowly and was mostly quiet. Flare: C1.6 at 19:23 UTC.
Region 10346 was quiet and stable.
Region 10348 developed moderately quickly and merged with region S151. The leading penumbra of region 10348 and the trailing penumbra of S151 became a single large penumbra creating a magnetic delta structure. M class flares are possible. Flares: C1.1 at 07:25 and C1.2 at 10:18 UTC.
Region 10349 decayed in the trailing and leading spot sections. Some penumbral growth was observed in the central spots but overall the region looks less threatening than it did a day ago. Flares: C1.3 at 02:00, C1.8 long duration event peaking at 03:01, C1.4 at 08:12, C1.3 at 13:49, C1.2 at 15:05 and C1.3 at 17:45 UTC.
Region 10351 was quiet and stable.
New region 10354 rotated into view on May 3 and was numbered the next day.
Spotted regions not yet numbered by SEC/NOAA:
[S154] A new region emerged in the northeast quadrant on May 4, due south of region 10354. Location at midnight: N12E59.
May 2-4: 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 recurrent coronal hole (CH38) in the southern hemisphere will rotate into a geoeffective position on May 2-5 and May 7.
Processed SOHO EIT 284 image at 19:06 UTC on May 4. Any black areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to unsettled early on May 5. Then a high speed stream from coronal hole CH38 will begin dominating the solar wind and cause unsettled to minor storm conditions until May 9. 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 stations tonight: Radio Cristal del Uruguay and Cadena Peruana de Noticias (strong signal).]
|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|
|10344||2003.04.24||6||N14W94||0120||DAO||rotated out of view|
area was 0850
formerly region S152
|10354||2003.05.04||1||1||N19E58||0040||HSX||formerly region S153|
|Total spot count:||92||105|
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||145.4 (1)||21.4 (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.