Last major update issued on September 13, 2007 at 03:05 UTC.
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The geomagnetic field was very quiet on September 12. Solar wind speed ranged between 273 and 304 km/s (average speed was 285 km/s, decreasing 4 km/s from the previous day).
Solar flux measured at 20h UTC on 2.8 GHz was 65.9. 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: 11010001 (planetary), 11121000 (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 10-12: 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 recurrent coronal hole (CH290) in the southern hemisphere was in an Earth facing position on September 10-11.
Processed STEREO 195 image at 19:15 UTC on September 12. 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 good. Propagation on long distance northeast-southwest paths is poor.
Monitoring remarks from a location near N58E06: September 11: Propagation was best to the northeastern USA and to Cuba. In particular New Hampshire was favored with occasionally excellent signals from 1250 WKBR, 1270 WTSN and 1290 WKBK. 1230 kHz had WESX and WCMC as the dominant signals.
The geomagnetic field is expected to be quiet on September 13. Some unsettled and active intervals are possible on September 14-15 due to effects from CH290. Quiet conditions are likely on September 16-20.
|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||67.5 (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.