Solar Terrestrial Activity Report

Last major update issued on August 18, 2010 at 03:30 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 July 3, 2010)]

Recent activity

The geomagnetic field was quiet on August 17. Solar wind speed ranged between 336 and 378 km/s. There was a minor but noticable discontinuity in solar wind speed, density and the IMF total field at about 23:20 UTC at ACE. This may have been associated with the arrival of a weak disturbance following the CME observed on August 14.

Solar flux measured at 20h UTC on 2.8 GHz was 81.1. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.8). Three hour interval K indices: 11112122 (planetary), 02121212 (Boulder).

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

At midnight UTC the visible solar disk had 2 spotted regions.

Region 11098 decayed and could soon become spotless.
Region 11100 was unchanged.

A C1.4 long duration event began late in the day and peaked at 00:05 UTC on August 18. Its origin was in region 11099 just behind the northwest limb. A CME was observed as well.

Coronal mass ejections (CMEs)

August 15-17: 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 large recurrent coronal hole (CH418) in the northern hemisphere will likely be Earth facing on August 19-22.

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 quiet with a chance of unsettled intervals on August 18. Quiet conditions are likely on August 19-21. A high speed stream associated with CH418 could cause quiet to active conditions on August 22-25.

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
11097 2010.08.10     N29W28           plage
11098 2010.08.11 5 3 N14W55 0010 BXO BXO  
11100 2010.08.16 1 1 S23E49 0010 AXX HRX  
Total spot count: 6 4  
SSN: 26 24  

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
2010.08 82.8 (1) 21.6 (2A) / 39.5 (2B) (19.5 predicted, +1.2) (9.03)

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.