Solar Terrestrial Activity Report

Last major update issued on August 9, 2011 at 04:25 UTC. Minor update posted at 17:55 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 8, 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 8. Solar wind speed ranged between 451 and 588 km/s under the influence of a high speed stream from CH469.

Solar flux measured at 20h UTC on 2.8 GHz was 101.5 (increasing 9.8 over the last solar rotation). The planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.5). Three hour interval K indices: 33233222 (planetary), 23233212 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight UTC the visible solar disk had 4 spotted regions.

Region 11263 became more complex as negative polarity flux emerged just south of the positive polarity spots in the central penumbra. What was a weak magnetic delta has quickly become a complex structure with positive polarity spots situated between the negative polarity spots in the north and south inside that penumbra. Further M class flaring is likely and there is a chance of an X class flare. Flares: C1.3 at 03:10, C2.2 at 16:36, M3.5/1B at 18:10 (associated with type II and IV radio sweeps and a fast CME. The CME was full halo in STEREO-A and possibly partial halo in LASCO images), C7.7 at 22:09, long duration C5.3 peaking at 23:22 UTC
Region 11266 developed slowly and quietly.
Region 11267 was quiet and stable
Region 11268 was quiet and stable.

Minor update added at 08:25 UTC on August 9: Region 11263 produced the largest flare of cycle 24, a major X6.9 event at 08:05 UTC. When available STEREO and LASCO images will be studied to determine if there was a potentially geoeffective CME associated with this event. There's a possibility of a significant proton event as well.

Minor update added at 14:15 UTC: The CME associated with the X6.9/2B flare was fast and wide. While the core CME won't impact Earth, there's a slight chance of a weak flank impact on August 11 or 12. The above 10 MeV proton event appears to have peaked near 30 pfu.

Minor update added at 17:55 UTC: Based on currently available LASCO imagery the CME developed into a full halo. The CME could impact Earth on August 11 and cause unsettled to active conditions with a chance of minor storm intervals.

Coronal mass ejections (CMEs)

August 6-7: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.
August 8: The M3.5 flare in region 11263 produced a fast CME which may be partially Earth directed.

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 (CH469) was Earth facing position on August 4-5.

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. Propagation on long distance northeast-southwest paths is fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 9 due to effects from CH469. Quiet conditions are likely on August 10. On August 11 the partial halo CME observed on August 8 could reach Earth, however, there's a chance the August 9 CME could reach us first. As the CMEs are from near limb events the disturbance level will likely reach unsettled to active with a chance of minor storming.

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
11263 2011.07.27
2011.07.28
13 18 N18W68 0450 EKC EKC

beta-gamma-delta

11266 2011.08.02
2011.08.04
20 18 N18W12 0050 DSI DSI  
S1152 2011.08.03     S07E01           plage
11267 2011.08.04
2011.08.05
5 7 S17W14 0010 BXO BXO

 

11268 2011.08.05
2011.08.06
2 4 N20E04 0000 AXX AXX location: N18E05
S1156 2011.08.06     S23W45           plage
S1157 2011.08.07     S20E62         plage
S1158 2011.08.07     S17W26         plage
Total spot count: 40 47  
Sunspot number: 80 87  (raw spot count + 10 * number of spotted regions)
Classification adjusted SN: 55 62  (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): 48 29  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
2011.08 113.6 (1) 23.3 (2A) / 90.4 (2B) (54.8 predicted, +4.2) (14.60)

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.