Last major update issued on September 18, 2006 at 03:25 UTC.
geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update September 3, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 3, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 3, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update September 8, 2006)]
The geomagnetic field was quiet to active on September 17. Solar wind speed ranged between 332 and 471 km/s (all day average 388 km/s - increasing 74 km/s over the previous day) under the influence of a moderately high speed stream from CH239.
Solar flux measured at 20h UTC on 2.8 GHz was 78.0. The planetary A index was 16 (STAR Ap - based on the mean of three hour interval ap indices: 15.8). Three hour interval K indices: 11244143 (planetary), 11254243 (Boulder).
The background x-ray flux is at the class A2 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.
Spotted regions not numbered by NOAA/SEC:
[S675] This region rotated into view at the southeast limb on September 16. Location at midnight: S08E61.
September 15-17: No obvious partly or fully Earth directed CMEs were detected in 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 trans equatorial coronal hole (CH239) was in an Earth facing position on September 13-14. A recurrent trans equatorial coronal hole (CH240) will likely rotate into an Earth facing position on September 20-22.
Processed SOHO/EIT 284 image at 19:06 UTC on September 17. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to active on September 18 under the influence of a high speed stream from CH239. Quiet to unsettled conditions are likely on September 19-22 becoming unsettled to minor storm on September 23-24 due to a high speed stream from CH240.
|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. The Newfoundland stations on 740, 750, 800 and 930 kHz all had fair to strong signals. From the USA only a few stations located in the Boston area (1030 and 1510 kHz) were noted with poor to fair signals. Some stations from Cuba and Colombia had fair to good signals as well. Propagation on long distance northeast-southwest paths is poor.
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
|Location at midnight||Area||Classification||Comment|
|10908||2006.09.05||1||S14W90||0120||HAX||rotated out of view|
|Total spot count:||1||1|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|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||81.8 (1)||16.7 (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.