Last major update issued on May 28, 2006 at 05:00 UTC.
[Solar and
geomagnetic data - last month (updated daily)]
[Solar wind and
electron fluence charts (updated daily)]
[Solar cycles 21-23
(last update April 1, 2006)]
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[Graphical comparison
of cycles 21, 22 and 23 (last update April 1, 2006)]
[Graphical
comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 1, 2006)]
[Historical solar and
geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update
May 3, 2006)]
The geomagnetic field was inactive to quiet on May 27. Solar wind speed ranged between 278 and 323 (all day average 292) km/sec. A minor disturbance began early on May 28. Solar wind speed remained low while density increased and the interplanetary magnetic field became stronger.
Solar flux measured at 20h UTC on 2.8 GHz was 83.0. The planetary A index
was 3 (STAR Ap - based on the mean of three hour interval ap
indices: 3.3).
Three hour interval K indices: 20001112 (planetary), 10100012 (Boulder).
The background x-ray flux is at the class A5 level.
At midnight there were 5 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.
Region 10886 gained a few small spots, however, the leader spot lost
some of its penumbral area.
Region 10887 decayed slightly and was quiet.
Region 10888 developed slowly and is rotating over the northwest limb.
New region 10889 emerged in the southeast quadrant.
Spotted regions not numbered by NOAA/SEC:
[S657] This region emerged in the southwest quadrant on May 27.
Location at midnight: S15W16.
May 27: No partly or fully Earth directed CMEs were observed in LASCO
imagery.
May 25/26: A very faint halo CME was observed in LASCO images early on
May 26. Its source was likely a B class event in region 10885 late on May 25.
This CME could reach Earth on May 29.
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 (CH226) will likely rotate into an Earth facing position on May 29-30.
Processed SOHO/EIT 284 image at 19:06 UTC on May 26. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to active on May 28-30, quiet to unsettled on May 31, becoming quiet to active on June 1-3 due to a high speed stream from CH226.
| 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. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at 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.
Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Radio Cristal del Uruguay again had the best signal. On other frequencies most of the staitons heard were from Argentina (950 kHz had the best signal) and Uruguay.
Compare to the previous day's image.
Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SEC. 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. SEC active region numbers in the table below and in the active region map above are the historic SEC/USAF numbers.
| Active region | Date numbered | SEC spot count |
STAR spot count |
Location at midnight | Area | Classification | Comment |
|---|---|---|---|---|---|---|---|
| 10884 | 2006.05.19 | S12W57 | plage | ||||
| 10885 | 2006.05.20 | 3 | S12W54 | 0050 | CRO | spotless | |
| 10886 | 2006.05.23 | 6 | 5 | N08W12 | 0050 | CSO | |
| 10887 | 2006.05.26 | 4 | 3 | S13E52 | 0050 | CRO | classification was BXO at midnight, area 0010 |
| 10888 | 2006.05.26 | 4 | 3 | N06W77 | 0090 | DAO | |
| 10889 | 2006.05.27 | 2 | 5 | S03E12 | 0020 | CRO | classification was CSO at midnight, area 0040 |
| S657 | 2006.05.27 | 7 | S15W16 | 0020 | BXI | ||
| Total spot count: | 19 | 23 | |||||
| SSN: | 69 | 73 | |||||
| Month | Average solar flux at Earth |
International sunspot number | Smoothed sunspot number |
|---|---|---|---|
| 2000.04 | 184.2 | 125.5 | 120.8 cycle 23 sunspot max. |
| 2000.07 | 202.3 | 170.1 | 119.8 |
| 2001.12 | 235.1 | 132.2 | 114.6 (-0.9) |
| 2005.02 | 97.2 | 29.2 | 33.9 (-0.7) |
| 2005.03 | 89.9 | 24.5 | 33.5 (-0.4) |
| 2005.04 | 86.0 | 24.2 | 31.6 (-1.9) |
| 2005.05 | 99.3 | 42.7 | 28.9 (-2.7) |
| 2005.06 | 93.7 | 39.3 | 28.8 (-0.1) |
| 2005.07 | 96.4 | 40.1 | 29.1 (+0.3) |
| 2005.08 | 90.5 | 36.4 | 27.4 (-1.7) |
| 2005.09 | 91.1 | 21.9 | 25.8 (-1.6) |
| 2005.10 | 77.0 | 8.5 | 25.5 (-0.3) |
| 2005.11 | 86.3 | 18.0 | (24.5 predicted, -1.0) |
| 2005.12 | 90.7 | 41.2 | (21.8 predicted, -2.7) |
| 2006.01 | 83.4 | 15.4 | (18.7 predicted, -3.1) |
| 2006.02 | 76.5 | 4.7 | (15.6 predicted, -3.1) |
| 2006.03 | 75.4 | 10.8 | (13.4 predicted, -2.2) |
| 2006.04 | 89.0 | 30.2 | (12.7 predicted, -0.7) |
| 2006.05 | 80.9 (1) | 32.2 (2) | (12.2 predicted, -0.5) |
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 (NOAA/SEC)
sunspot number. The official international sunspot number is typically
30-50% lower.
This report has been prepared by Jan Alvestad. It is based partly on my own observations and analysis, and partly on data from some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.
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