Solar Terrestrial Activity Report

Last major update issued on October 1, 2009 at 03:45 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-23 (last update October 4, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 4, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 4, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update September 13, 2009)]

Recent activity

The geomagnetic field was quiet on September 30. Solar wind speed ranged between 286 and 346 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 72.0. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 11111021 (planetary), 21213121 (Boulder).

The background x-ray flux is below the class A1 level.

At midnight there was 1 spotted region on the visible solar disk.

Region 11027 decayed further and lost penumbra on the single spot. The region will soon rotate out of view.

Coronal mass ejections (CMEs)

September 28-30: No partially or fully Earth directed CMEs were observed in LASCO or STEREO imagery.

Coronal holes

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 recurrent extension (CH381) of the northern polar coronal hole was in an Earth facing position on September 28. CH381 was marginally geoeffective during the previous rotation.

Processed SOHO/EIT 195 image at 23:12 UTC on September 30. The darkest areas on the solar disk are likely coronal holes.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on October 1-7. There's a chance of isolated unsettled intervals on October 1 due to possible effects from CH381.

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.

Active solar regions (Recent map)

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 SWPC
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
11026 2009.09.21     S34W47     plage
11027 2009.09.22 1 1 N23W76 0010 AXX  
Total spot count: 1 1  
SSN: 11 11  

Monthly solar cycle data

Month Average solar
flux at Earth
International sunspot number (SIDC) Smoothed sunspot number
2000.04 184.2 125.5 120.8
cycle 23 sunspot max.
2000.07 202.3 170.1 119.8
2001.12 235.1 132.2 114.6 (-0.9)
2008.06 65.8 3.4 3.2 (-0.3)
2008.07 65.7 0.5 2.8 (-0.4)
2008.08 66.5 0.5 2.6 (-0.2)
2008.09 67.1 1.1 2.3 (-0.3)
2008.10 68.3 2.9 1.83 (-0.5)
2008.11 68.6 4.1 1.75 (-0.08)
 
2008.12 69.2 0.8 1.7 (-0.05)
probably the sunspot minimum
2009.01 69.8 1.3 1.8 (+0.1)
2009.02 70.0 1.4 1.9 (+0.1)
2009.03 69.2 0.7 (2.0 predicted, +0.1)
2009.04 69.7 1.2 (2.3 predicted, +0.3)
2009.05 70.5 2.9 (2.6 predicted, +0.3)
2009.06 68.6 2.6 (3.1 predicted, +0.5)
2009.07 68.2 3.5 (3.9 predicted, +0.8)
2009.08 67.3 0.0 (4.7 predicted, +0.8)
2009.09  70.5 (1) 6.9 (2) (5.8 predicted, +1.1)

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/SWPC) 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.