Last major update issued on September 29, 2007 at 03:25 UTC.
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The geomagnetic field was quiet to minor storm on September 28. Solar wind speed ranged between 475 and 586 km/s (average speed was 550 km/s, increasing 138 km/s over the previous day) under the influence of a high speed stream from CH292.
Solar flux measured at 20h UTC on 2.8 GHz was 67.2. The planetary A index was 21 (STAR Ap - based on the mean of three hour interval ap indices: 21.4). Three hour interval K indices: 44432245 (planetary), 34432234 (Boulder).
The background x-ray flux is below the class A1 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.
New region 10971 emerged in the northeast quadrant on September 27 and was numbered the next day by NOAA/SEC.
September 26-28: 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 (CH292) in the southern hemisphere was an Earth facing position on September 24-25. Another recurrent coronal hole (CH293) in the southern hemisphere will be in an Earth facing position on September 29.
Processed SOHO/EIT 195 image at 22:24 UTC on September 28. 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 poor. Propagation on long distance northeast-southwest paths is fair.
Monitoring remarks from a location near N58E06: September 26-27: At 22h UTC all the usual Newfoundland and Nova Scotia stations were audible at good levels. A few minutes later stations from the northeastern USA (like 1390 WEGP and 1470 WLAM) became audible and at 23h UTC most of the New York 50 kW stations had strong signals. On 1470 kHz WWNN had become the dominant signal. Stations from Puerto Rico and Venezuela and a few from Brazil were heard well too.
The geomagnetic field is expected to be quiet to minor storm on September 29 and quiet to unsettled on September 30 and October 1. October 2 could see a few unsettled and active intervals due to effects from CH293. Generally quiet conditions are expected for October 3-16.
|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|
|10971||2007.09.28||5||3||N03E07||0040||CRO||formerly region S708|
|Total spot count:||5||3|
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||67.1 (1)||3.7 (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.