Last major update issued on September 19, 2007 at 02:50 UTC.
geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-23 (last update July 23, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 23, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 23, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update July 1, 2007)]
The geomagnetic field was quiet on September 18. Solar wind speed ranged between 295 and 338 km/s (average speed was 320 km/s, increasing 14 km/s over the previous day).
Solar flux measured at 20h UTC on 2.8 GHz was 66.5. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.9). Three hour interval K indices: 21001211 (planetary), 22001110 (Boulder).
The background x-ray flux is below the class A1 level.
At midnight the visible solar disk was spotless. The solar flare activity level was very low. No C class events were recorded during the day.
September 16-18: No obvious fully or partly Earth directed CMEs were observed in LASCO imagery.
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 large, recurrent trans equatorial coronal hole (CH291) will rotate into an Earth facing position on September 16-21.
Processed STEREO 195 image at 20:55 UTC on September 18. The darkest areas on the solar disk are likely coronal holes.
Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very good. Propagation on long distance northeast-southwest paths is poor.
Monitoring remarks from a location near N58E06: September 18: Lots of stations from the eastern half of Canada and USA were heard with good to excellent signals with the best propagation above 900 kHz. The Quebec province stations on 1610 and 1650 kHz both had signal peaks near S9+10dB.
The geomagnetic field is expected to be quiet initially on September 19. A high speed stream from CH291 could arrive later in the day or on September 20. The associated disturbance is expected to peak on September 21-22 at active to minor storm levels. Quiet to active conditions are likely on September 20 and 23-24.
|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/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|
|Total spot count:||0||0|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2007.03||72.2||4.8||(11.1 predicted, -0.5)|
|2007.04||72.4||3.7||(10.7 predicted, -0.4)|
|2007.05||74.4||11.7||(10.2 predicted, -0.5)|
|2007.06||73.7||12.0||(10.0 predicted, -0.2)|
|2007.07||71.6||10.0||(10.0 predicted, +0.0)|
|2007.08||69.1||6.2||(10.3 predicted, +0.3)|
|2007.09||67.3 (1)||3.2 (2)||(11.5 predicted, +1.2)|
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.