Solar Terrestrial Activity Report

Last major update issued on July 26, 2010 at 05:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update July 2, 2010)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update July 3, 2010)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update July 4, 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 to unsettled on July 25. Solar wind speed ranged between 331 and 460 km/s under the influence of a stream from CH415.

Solar flux measured at 20h UTC on 2.8 GHz was 85.2. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.0). Three hour interval K indices: 21112112 (planetary), 32112222 (Boulder).

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

At midnight there were 2 spotted regions on the visible solar disk.

Region 11089 decayed slowly and quietly.
Region 11090 added a couple of spots, then decayed late in the day.

Coronal mass ejections (CMEs)

July 23-25: 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 coronal hole (CH415) in the northern hemisphere will be Earth facing on July 21-26.

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.

Forecast

The geomagnetic field is expected to be quiet to unsettled on July 26-30 due to effects from CH415.

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
11089 2010.07.19 16 19 S24W08 0140 DSI DSI  
S790 2010.07.21     N14E02           plage
11090 2010.07.24 3 3 N23E43 0010 BXO BXO  
Total spot count: 19 22  
SSN: 39 42  

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
2009.05 70.5 2.9 2.3 (+0.1) 4.75
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 (9.2 predicted, +0.9) 2.93 / 3.07
2010.02 84.7 18.8 (10.4 predicted, +1.2) 4.15 / 4.61
2010.03 83.4 15.4 (12.1 predicted, +1.7) 4.58 / 4.65
2010.04 75.9 7.9 (13.7 predicted, +1.6) 10.22 / 10.24
2010.05 73.8 8.8 (15.0 predicted, +1.3) 9.18 / 8.15
2010.06 72.5 13.5 (16.4 predicted, +1.4) 8.17 / 6.85
2010.07 78.8 (1) 18.1 (2) (18.0 predicted, +1.6) (5.42)

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2) 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.
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 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.