Last major update issued on May 25, 2010 at 03:25 UTC.
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[Solar cycles 21-23 (last update October 4, 2007)]
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[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 4, 2007)]
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[Archived reports (last update April 2, 2010)]
The geomagnetic field was very quiet on May 24. Solar wind speed ranged between 276 and 361 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 72.6. The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.4). Three hour interval K indices: 10000111 (planetary), 00000111 (Boulder).
The background x-ray flux is at the class A3 level.
At midnight there were 2 spotted regions on the visible solar disk.
Region 11072 decayed further and was quiet.
Spotted regions not numbered by NOAA/SWPC:
[S767] This region emerged in the southwest quadrant on May 24 and
will rotate out of view late today. Location at midnight: S15W72.
May 22: No obvious Earth directed CMEs were observed in LASCO or
STEREO
images.
May 23: A full halo CME was observed in LASCO images after a
filament eruption in the northwest quadrant, this was associated with a long
duration B1.3 event peaking at 18:01 UTC.
May 24: A partial halo CME was observed in LASCO images and was associated
with another filament eruption in the same location as one day earlier.
Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago:
28 days ago
27 days ago
26 days ago
A small coronal hole (CH405) in the southern hemisphere rotated across the central meridian on May 20. A well defined recurrent coronal hole (CH406) in the northern hemisphere will likely rotate into an Earth facing position on May 27-28.
Processed SOHO/EIT 195 image at 00:00 UTC on May 25. The darkest areas on the solar disk are likely coronal holes.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet on May 25 with possible unsettled intervals should a low speed stream from CH406 arrive. Late on May 26 or early on May 27 quiet to active conditions are possible as a CME observed on May 23 is likely to reach Earth.
| 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.
Compare to the previous day's image
Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. 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 SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.
| Active region | Date numbered | SWPC spot count |
STAR spot count |
Location at midnight | Area | SWPC Classification |
Comment |
|---|---|---|---|---|---|---|---|
| 11072 | 2010.05.21 | 7 | 4 | S15W22 | 0090 | CSO | |
| S767 | 2010.05.24 | 2 | S15W72 | 0010 | BXO | ||
| Total spot count: | 7 | 6 | |||||
| SSN: | 17 | 26 | |||||
| Month | Average measured solar flux | International sunspot number (SIDC) | Smoothed sunspot number | Average ap (3) |
|---|---|---|---|---|
| 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) | |
| 2008.07 | 65.7 (SF minimum) | 0.5 | 2.8 (-0.4) | |
| 2008.12 | 69.2 | 0.8 | 1.7 (-) sunspot minimum |
3.25 |
| 2009.03 | 69.2 | 0.7 | 2.0 (+0.1) | 4.85 |
| 2009.04 | 69.7 | 1.2 | 2.2 (+0.2) | 4.52 |
| 2009.05 | 70.5 | 2.9 | 2.3 (+0.1) | 4.75 |
| 2009.06 | 68.6 | 2.6 | 2.7 (+0.4) | 5.22 |
| 2009.07 | 68.2 | 3.5 | 3.6 (+0.9) | 5.49 / 4.55 |
| 2009.08 | 67.3 | 0.0 | 4.8 (+1.2) | 5.70 / 4.89 |
| 2009.09 | 70.5 | 4.2 | 6.1 (+1.3) | 3.88 / 3.61 |
| 2009.10 | 72.6 | 4.6 | 7.0 (+0.9) | 3.66 / 3.56 |
| 2009.11 | 73.6 | 4.2 | (7.7 predicted, +0.7) | 2.45 / 2.63 |
| 2009.12 | 76.7 | 10.6 | (8.9 predicted, +1.2) | 1.41 / 1.92 |
| 2010.01 | 81.1 | 13.1 | (10.2 predicted, +1.3) | 2.93 / 3.07 |
| 2010.02 | 84.7 | 18.6 | (11.8 predicted, +1.6) | 4.15 / 4.61 |
| 2010.03 | 83.4 | 15.4 | (13.7 predicted, +1.9) | 4.58 / 4.65 |
| 2010.04 | 75.9 | 7.9 | (15.3 predicted, +1.8) | 10.22 / 10.24 |
| 2010.05 | 74.0 (1) | 14.0 (2) | (16.6 predicted, +1.3) | (8.01) |
1) Running average based on the
daily 20:00 UTC observed solar flux
value at 2800 MHz.
2) Current impact on the monthly SSN based on the Boulder (NOAA/SWPC) sunspot number
(accumulated daily sunspots / month days). The official international sunspot number is typically
30-50% lower.
3) Running average based on the
daily SWPC ap indices. Values in red are based on
the
official NGDC ap indices.
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.