Last major update issued on September 16, 2007 at 01:35 UTC.
geomagnetic data - last month (updated daily)]
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[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 23, 2007)]
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The geomagnetic field was quiet on September 15. Solar wind speed ranged between 342 and 416 km/s (average speed was 365 km/s, increasing 66 km/s over the previous day) under the influence of a weak low speed stream from CH290.
Solar flux measured at 20h UTC on 2.8 GHz was 67.7. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.1). Three hour interval K indices: 21011112 (planetary), 22011122 (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 13-15: 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. A recurrent trans equatorial coronal hole (CH291) will likely rotate into an Earth facing position on September 17-21.
Processed STEREO 195 image at 21:15 UTC on September 15. 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 15-16: Stations like 800 VOWR, 930 CJYQ and 1070 CBA were audible as early as 21:45 UTC. Between 22 and 23h UTC several stations from Brazil could be heard with weak signals. After 23:30 UTC many stations from the northeastern USA had fair to good signals. During the morning signals were weaker than on the previous day and there were more stations from northern South America.
The geomagnetic field is expected to be quiet on September 16-19. A high speed stream from CH291 could cause quiet to active conditions on September 20-24, with a chance of a few minor storm intervals.
|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||67.4 (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.