Solar Terrestrial Activity Report

Last major update issued on September 6, 2010 at 03:10 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)]

Recent activity

The geomagnetic field was quiet to unsettled on September 5. Solar wind speed ranged between 285 and 349 km/s. A low speed stream from CH420 began to influence the field after 18h UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 82.1 (down 2.0 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.9). Three hour interval K indices: 00000113 (planetary), 00111113 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight UTC the visible solar disk had 3 spotted regions.

Region 11101 was quiet and is rotating out of view at the northwest limb.
Region 11105 developed in the leading spot section while decay was observed in the trailing and intermediate spots. C flares are possible.

Spotted regions not numbered by NOAA/SWPC:
[S809] Small spots emerged in the northeast quadrant in a plage area that rotated into view several days ago. Location at midnight: N17E02

Coronal mass ejections (CMEs)

September 3-5: No obviously Earth directed CMEs were seen in LASCO or STEREO images.

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 trans equatorial coronal hole (CH420) was Earth facing on September 1.

Image courtesy of SDO (NASA) and the AIA consortium. Annotations are my own. 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 poor to fair. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on September 6 due to effects from CH420. Quiet conditions are likely on September 7-8.

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 Spot count Location at midnight Area Classification SDO (NASA) / AIA 4500
image
Comment
SWPC STAR SWPC STAR Current Previous
11101 2010.08.24 1 1 N13W88 0120 HSX HSX   location: N12W83
11103 2010.09.01 1   N25W90 0010 AXX     rotated out of view
S806 2010.09.01     N21W46           plage
11105 2010.09.02 26 22 N19W52 0130 DRI DAI  
 
S808 2010.09.03     N02W10          
plage
S809 2010.09.05   2 N17E02 0000   AXX    
 
Total spot count: 28 25  
SSN: 58 55  

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
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)  
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
3.25
2009.06 68.6 2.9 2.7 (+0.4) 5.22
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
2010.09 79.0 (1) 8.9 (2A) / 53.6 (2B) (20.7 predicted, +1.2) (4.55)

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.