Solar Terrestrial Activity Report

Last major update issued on August 12, 2011 at 03:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update August 2, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 2, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 2, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update August 2, 2011)]

[POES auroral activity level since October 2009 - updated August 11, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2110 [May-June 2011] - 2111 [June-July 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on August 11. Solar wind speed ranged between 354 and 454 km/s. A weak disturbance was observed beginning near 20h UTC at SOHO, possibly related to the partial halo CME observed on August 8.

Solar flux measured at 20h UTC on 2.8 GHz was 84.2 (decreasing 9.6 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.6). Three hour interval K indices: 11111123 (planetary), 12212212 (Boulder).

The background x-ray flux is at the class B3 level.

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

Region 11266 decayed slowly and quietly.
Region 11268 decayed slowly and quietly.
New region 11269 rotated into view at the northeast limb on August 10 and was numbered the next day by SWPC.
New region 11270 emerged in the southeast quadrant on August 10 and got an SWPC number the following day.

Spotted regions not numbered by NOAA/SWPC:
[S1159] emerged in the northeast quadrant on August 9. Location at midnight: N17E27

Coronal mass ejections (CMEs)

August 10-11: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.
August 9: The X6.9 event in region 11263 was associated with a fast full halo CME.

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 (CH471) will rotate into an Earth facing position on August 11-13.

The above coronal hole map is based on a new method where coronal holes are detected automatically. The method may need some fine tuning, however, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using the new method, the extent and intensity of both holes are consistent with other data sources.

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 August 12 and quiet on August 13. A high speed stream from CH471 could cause unsettled to minor storm conditions on August 14-16.

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

(Click on image for higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.

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
detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
11266 2011.08.02
2011.08.04
2 1 N19W49 0010 AXX AXX area: 0000
S1152 2011.08.03     S07W38           plage
11267 2011.08.04
2011.08.05
    S15W57         plage
11268 2011.08.05
2011.08.06
  1 N18W34 0000   AXX  
S1157 2011.08.07     S20E23           plage
S1158 2011.08.07     S19W66         plage
S1159 2011.08.09   2 N17E27 0000   BXO  
S1160 2011.08.09     N09E00           plage
11270 2011.08.10
2011.08.11
2 2 N23E54 0020 DSO HRX formerly region S1161
S1162 2011.08.10     S23E26         plage
11269 2011.08.10
2011.08.11
2 5 S22E17 0020 DRO BXO formerly region S1163
Total spot count: 6 11  
Sunspot number: 36 61  (raw spot count + 10 * number of spotted regions)
Classification adjusted SN: 14 14  (Sum of raw spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 22 20  k * (sunspot number). k = 0.6 for SWPC. k = 0.33 for STAR SDO

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
3.25
2010.05 73.8 8.7 15.5 (+1.5) 9.18 / 8.15
2010.06 72.5 13.6 16.4 (+0.9) 8.17 / 6.85
2010.07 79.8 16.1 16.7 (+0.3) 6.31 / 5.15
2010.08 79.2 19.6 17.4 (+0.7) 8.49 / 7.77
2010.09 81.1 25.2 19.6 (+2.2) 5.33 / 5.45
2010.10 81.6 23.5 23.2 (+3.6) 6.07 / 6.27
2010.11 82.5 21.5 26.5 (+3.3) 4.80 / 5.50
2010.12 84.2 14.4 28.8 (+2.3) 3.41 / 4.35
2011.01 83.6 19.1 31.0 (+2.2) 4.32 / 5.51
2011.02 94.6 29.4 (33.6 predicted, +2.6) 5.41 / 6.44
2011.03 115.0 56.2 (36.6 predicted, +3.0) 7.79 / 8.18
2011.04 112.6 54.4 (39.4 predicted, +2.8) 9.71 / 8.83
2011.05 95.8 41.6 (42.7 predicted, +3.3) 9.18 / 8.94
2011.06 95.8 37.0 (46.5 predicted, +3.8) 8.96
2011.07 94.2 43.9 (50.6 predicted, +4.1) 9.14
2011.08 107.4 (1) 27.6 (2A) / 77.8 (2B) (54.8 predicted, +4.2) (12.55)

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 SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the preliminary 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.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.