Solar Terrestrial Activity Report

Last major update issued on September 2, 2010 at 04:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update August 3, 2010)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 3, 2010)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 3, 2010)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update August 23, 2010)]

Recent activity

The geomagnetic field was quiet on September 1. Solar wind speed ranged between 299 and 353 km/s. A low speed stream, likely from CH419 began influencing the field early in the day, however, the IMF was mostly northwards until 16h UTC. Later in the day the weak disturbance caused a minor increase in geomagnetic activity.

Solar flux measured at 20h UTC on 2.8 GHz was 76.3 (down 6.4 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.1). Three hour interval K indices: 10000222 (planetary), 11110122 (Boulder).

The background x-ray flux is at the class A6 level.

At midnight UTC the visible solar disk had 5 spotted regions.

Region 11101 was quiet and displayed no significant changes.
Region 11102 was quiet and decayed slowly.
New region 11103 emerged in the northwest quadrant.

Spotted regions not numbered by NOAA/SWPC:
[S806] This region emerged in the northern hemisphere near the central meridian on September 1. Location at midnight: N21W07
[S807] A new region emerged late in the day near the central meridian in the northern hemisphere. Location at midnight: N19E03

Coronal mass ejections (CMEs)

August 30 - September 1: 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 trans equatorial coronal hole (CH419) was Earth facing on August 27-28. 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be mostly quiet on September 2-3. On September 2 there's a chance of unsettled intervals due to effects from CH419. Quiet to active conditions are possible on September 4-5 due to effects from CH420.

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 2 3 N12W32 0150 CSO CSO  
S804 2010.08.26     S07W63           plage
11102 2010.08.29 5 9 N26W52 0100 CAO CAO area: 0060
11103 2010.09.01 2 1 N25W32 0010 BXO HRX    
11104 2010.09.01 2   N24W27 0010 BXO       spotless at midnight
S806 2010.09.01   2 N21W07 0010   BXO    
S807 2010.09.01   1 N19E03 0010   AXX    
Total spot count: 11 16  
SSN: 51 66  

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 predicted, +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 (15.3 predicted, +1.4) 9.18 / 8.15
2010.06 72.5 13.5 (16.7 predicted, +1.4) 8.17 / 6.85
2010.07 79.8 16.1 (18.3 predicted, +1.6) 6.31 / 5.15
2010.08 79.2 28.2 (2A) / 28.2 (2B) (19.5 predicted, +1.2) 8.49
2010.09 76.3 (1) 1.7 (2A) / 51.0 (2B) (20.8 predicted, +1.3) (4.13)

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.