Last major update issued on September 1, 2007 at 02:40 UTC.
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The geomagnetic field was quiet to unsettled on August 31. Solar wind speed ranged between 348 and 415 km/s (average speed was 372 km/s, decreasing 50 km/s from the previous day). A relatively low speed stream from CH288 arrived at ACE at about 19h UTC.
Solar flux measured at 20h UTC on 2.8 GHz was 70.9. The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.9). Three hour interval K indices: 11122233 (planetary), 22121233 (Boulder).
The background x-ray flux is below the class A1 level.
At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.
Region 10969 developed early in the day, then decayed slowly.
Spotted regions not numbered by NOAA/SEC:
[S707] This region emerged in the southeast quadrant on August 31. Location at midnight: S05E09
August 29-31: No obvious fully or partly Earth directed CMEs were observed in incomplete 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 (CH288) in the southern hemisphere was in an Earth facing position on August 28-29, however, most of the coronal hole is too far to the south to contribute to a geomagnetic disturbance.
Processed STEREO 195 image at 19:15 UTC on August 31. 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 fair. Propagation on long distance northeast-southwest paths is fair.
Monitoring remarks from a location near N58E06: August 31 - September 1: Relatively strong signals were noted from many TA stations from Newfoundland in the north to Argentina in the south. 1350 Radio Buenos Aires was excellent at 23:15 UTC while at the same time 1400 CBG was strong. Later on lots of signals from the USA (east coast), the Caribbean and northern South America were audible at fair to good levels.
The geomagnetic field is expected to be quiet to unsettled on September 1-2 due to effects from CH288. Mostly quiet conditions are likely on September 3-5.
|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:||4||6|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2007.02||77.7||10.6||(11.6 predicted, -0.4)|
|2007.03||72.2||4.8||(11.1 predicted, -0.5)|
|2007.04||72.4||3.7||(10.8 predicted, -0.3)|
|2007.05||74.4||11.7||(10.4 predicted, -0.4)|
|2007.06||73.7||12.0||(10.3 predicted, -0.1)|
|2007.07||71.6||10.0||(10.5 predicted, +0.2)|
|2007.08||69.1 (1)||9.9 (2)||(11.0 predicted, +0.5)|
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.