Last major update issued on September 27, 2006 at 03:30 UTC.
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The geomagnetic field was quiet to unsettled on September 26. Solar wind speed ranged between 461 and 555 km/s (all day average 497 km/s - decreasing 75 km/s from the previous day) under the diminishing influence of a high speed stream from CH240.
Solar flux measured at 20h UTC on 2.8 GHz was 70.7. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.8). Three hour interval K indices: 23201112 (planetary), 24211111 (Boulder).
The background x-ray flux is at the class A1 level.
At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.
New region 10911 emerged near the northeast limb. The region appeared to be decaying late in the day.
September 24-26: No obvious partly or fully Earth directed CMEs were detected in incomplete LASCO imagery.
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 recurrent coronal hole (CH241) in the southern hemisphere will be in an Earth facing position on September 25-27.
Processed SOHO/EIT 284 image at 19:06 UTC on September 26. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be generally quiet on September 27 and most of September 28. Quiet to active conditions are likely from late on September 28 until September 30 due to a high speed stream from CH241. Occasional minor storm intervals are possible.
| 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 to fair. Propagation on long distance northeast-southwest paths is poor.
Several stations from the Canadian Atlantic provinces and the northeast US were heard with fair to good signals. Some stations from the Caribbean and the northeastern part of South America were noted as well, one example being Radio Senda (1680 kHz) from the Dominican Republic with the best signal I've heard from them.
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 |
|---|---|---|---|---|---|---|---|
| 10910 | 2006.09.18 | S08W59 | plage | ||||
| 10911 | 2006.09.26 | 3 | 1 | N07E72 | 0030 | BXO | classification was AXX at midnight, area 0010 |
| Total spot count: | 3 | 1 | |||||
| SSN: | 13 | 11 | |||||
| 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) |
| 2005.07 | 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 | 24.9 (-0.6) |
| 2005.12 | 90.7 | 41.2 | 23.0 (-1.9) |
| 2006.01 | 83.4 | 15.4 | 20.8 (-2.2) |
| 2006.02 | 76.5 | 4.7 | 18.6 (-2.2) |
| 2006.03 | 75.4 | 10.8 | (17.1 predicted, -1.5) |
| 2006.04 | 89.0 | 30.2 | (16.4 predicted, -0.7) |
| 2006.05 | 80.9 | 22.2 | (15.9 predicted, -0.5) |
| 2006.06 | 76.5 | 13.9 | (14.1 predicted, -1.8) |
| 2006.07 | 75.7 | 12.2 | (12.4 predicted, -1.7) |
| 2006.08 | 79.0 | 12.9 | (11.9 predicted, -0.5) |
| 2006.09 | 78.2 (1) | 20.4 (2) | (11.9 predicted, -0.0) |
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 (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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