Last major update issued on September 26, 2010 at 04:25 UTC.
[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update September 4, 2010)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 4, 2010)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 4, 2010)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update September 4, 2010)]
The geomagnetic field was quiet to unsettled on September 25. Solar wind speed ranged between 450 and 633 km/s under the influence of a high speed stream from CH422. Wind speed decreased gradually after noon as the coronal hole effects diminished.
Solar flux measured at 20h UTC on 2.8 GHz was 82.9 (up 9.0 over the last solar rotation). The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.1). Three hour interval K indices: 33211111 (planetary), 23322111 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight UTC the visible solar disk had 3 spotted regions.
Region 11108 decayed slowly and quietly.
Region 11109 developed early in the day, then decayed slowly. C flares are possible.
Spotted regions not numbered by NOAA/SWPC:
[S816] Several small spots emerged early in the day in a new region just west of AR 11109. Location at midnight: N19E16
September 23-25: No obviously Earth directed CMEs were seen in LASCO or STEREO images.
Coronal hole 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 small trans equatorial, recurrent coronal hole (CH423) was in an Earth facing position on September 24.
Image courtesy of SDO (NASA) and the AIA consortium. Annotations are my own. The darkest areas on the solar disk are likely coronal holes.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor to fair. Propagation on long distance northeast-southwest paths is poor to fair.
The geomagnetic field is expected to be quiet on September 26-27 and quiet to unsettled on September 28 when effects from CH423 are possible.
|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/SWPC. 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 SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.
|Active region||Date numbered||Spot count||Location at midnight||Area||Classification||SDO (NASA) / AIA 4500
|Total spot count:||20||31|
|Month||Average measured solar flux||International sunspot number (SIDC)||Smoothed sunspot number||Average ap
cycle 23 sunspot max.
|2008.07||65.7 (SF minimum)||0.5||2.8 (-0.4)|
|2009.07||68.2||3.2||3.6 (+0.9)||5.49 / 4.55|
|2009.08||67.3||0.0||4.8 (+1.2)||5.70 / 4.89|
|2009.09||70.5||4.3||6.2 (+1.4)||3.88 / 3.61|
|2009.10||72.6||4.8||7.1 (+0.9)||3.66 / 3.56|
|2009.11||73.6||4.1||7.6 (+0.5)||2.45 / 2.63|
|2009.12||76.7||10.8||8.3 (+0.7)||1.41 / 1.92|
|2010.01||81.1||13.2||9.3 (+1.0)||2.93 / 3.07|
|2010.02||84.7||18.8||10.6 (+1.3)||4.15 / 4.61|
|2010.03||83.4||15.4||(12.3 predicted, +1.7)||4.58 / 4.65|
|2010.04||75.9||7.9||(13.9 predicted, +1.6)||10.22 / 10.24|
|2010.05||73.8||8.8||(15.2 predicted, +1.3)||9.18 / 8.15|
|2010.06||72.5||13.5||(16.6 predicted, +1.4)||8.17 / 6.85|
|2010.07||79.8||16.1||(18.3 predicted, +1.7)||6.31 / 5.15|
|2010.08||79.2||19.6||(19.5 predicted, +1.2)||8.49 / 7.77|
|2010.09||80.1 (1)||26.8 (2A) / 32.2 (2B)||(20.7 predicted, +1.2)||(5.41)|
1) Running average based on the
daily 20:00 UTC observed solar flux
value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the daily SWPC ap indices. Values in red are based on the official NGDC ap indices.
This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.